1 40 381 https://bereket-haileab.geology.sites.carleton.edu/files/original/dd032a82b62cffef71e152d0e158c962.jpg f0bfdcf1740ee7624fe2cfd7c10156e0 https://bereket-haileab.geology.sites.carleton.edu/files/original/90ff65076008377f4814de77960e1589.jpg 02aed0b04a41c237be87b3704ad6f6c6 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-1 Subject The topic of the resource Garnet–Sillimanite Schist (High-Grade Metamorphic Rock) Description An account of the resource Mineralogy Major Minerals: Sillimanite (including fibrolite) Garnet Quartz Minor Minerals: Muscovite Biotite Albite Orthoclase Zircon (accessory, often included in garnet) Texture & Fabric Strong foliation (schistosity) defined by aligned micas and fibrolitic sillimanite Slender prismatic and fibrous sillimanite forming mats and bundles Porphyroblastic texture with garnet crystals embedded in a foliated matrix Deformed garnets: flattened, elongated, and sometimes fractured Quartz inclusion-rich garnets, with trails recording earlier fabrics Growth zoning in garnets, indicating evolving metamorphic conditions BH250-1 is a striking example of a high-grade metamorphic rock that records both intense deformation and elevated temperature conditions deep within the continental crust. This rock is dominated by abundant sillimanite, occurring both as slender prismatic crystals and as fine fibrous aggregates known as fibrolite, intergrown with quartz and micas. One of the most distinctive features of this specimen is the presence of garnet porphyroblasts that have undergone significant deformation. While many garnets originally formed as euhedral, equant crystals, they are now commonly flattened, elongated, and stretched parallel to the rock’s foliation. In some cases, the foliation wraps through or even cuts across the garnets, indicating that deformation continued after or during garnet growth. This provides strong evidence for syn- to post-tectonic deformation. The garnets contain abundant quartz inclusions concentrated in their central cores, often arranged in trails or patterns that preserve earlier fabrics. In contrast, the outer rims of the garnets are largely inclusion-free, suggesting a later stage of crystal growth. These inclusion-rich cores are key to interpreting the rock’s history: They likely represent pre-existing foliation (S₁) that became trapped during early garnet growth. Their orientation relative to the external foliation helps reconstruct the rotational and deformational history of the porphyroblasts. The presence of inclusion-poor rims indicates that the garnets likely continued to grow after peak metamorphic conditions, during a later stage when deformation had diminished and fewer inclusions were incorporated. Many garnets also show growth zoning, reflecting changes in pressure–temperature–chemical conditions during crystallization. Taken together, the inclusion-rich cores and inclusion-free rims, along with zoning patterns, suggest that these garnets began forming as pre- to syn-tectonic porphyroblasts, and subsequently experienced post-peak (retrograde or late-stage) growth, followed by continued deformation that modified their overall shape and fabric. Metamorphic Interpretation This rock formed under upper amphibolite to granulite facies conditions, where temperatures are sufficiently high for the formation of sillimanite. Its mineral assemblage and textures indicate: High temperature metamorphism (sillimanite stability field) Likely moderate to high pressures typical of continental collision zones Prolonged deformation, resulting in: Rotation and flattening of garnets Development of strong foliation Overprinting of earlier mineral growth This combination suggests a tectonically active environment, such as a continental orogen, where rocks are buried, heated, deformed, and exhumed. In addition, the original bulk composition of this rock was clearly pelitic, as indicated by the abundance of sillimanite, muscovite, and plagioclase. This mineral assemblage is characteristic of aluminum-rich sedimentary protoliths (such as shale or mudstone), further supporting an origin tied to metamorphism of fine-grained sedimentary material under high-temperature conditions Geologic Significance BH250-1 is an excellent teaching example because it preserves a multi-stage metamorphic history: 1. Initial mineral growth (garnet porphyroblasts with inclusion trails) 2. Development of foliation and alignment of sillimanite and micas 3. Continued deformation, flattening garnets and modifying textures It clearly demonstrates how metamorphic rocks can act as records of both pressure–temperature conditions and deformation history, making it ideal for interpreting tectonic processes in deep crustal environments. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-1. Housed at Carleton College in Minnesota. Contributor An entity responsible for making contributions to the resource Bereket Haileab Carl Tape, '01 Type The nature or genre of the resource Thin section and hand sample Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Alaska, USA Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=2681884ea4c4495fa3ec883c6366e7fb" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=2681884ea4c4495fa3ec883c6366e7fb">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1V_mvQitTvu6rEifol4D4zNCyb8xgwNfU/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1gC-CetpErmkVNkyrvdKP4RjFa6Z0yc2k/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1VM-IKcOzRFCQTOA6mDh33vKCTfHySwSh/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1JuKBZ3vh3HK_oW8ha6cz-0Z7xtfhYT7t/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/18iXDSJMGTxZ-hR0dW10r1EDuLB83H3ze/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1dfLPT8oawB5eV9RjOYnKINhJ3-tyYw73/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1mr_zzHj3cMwm9HDwFjA4rN3UJxOrmYBc/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1bh0PjYlONnb_0E24xSXxObKcKUsPqIi9/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Z0dbTA0qFiR_6Zq3bSXICY5LTiOgyG4g/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1RUdwS0tfEGoZs_rqjVGd3BJrFuDkgVV9/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1asq39_wTqq2TZCifrjETvNZ3fMexDrzR/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1BfrouU6DUC9DaavpK7nWMqF36OjlVJ-T/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1cNYTOqv67hi5csRzOMXmTBcfGi1DnBjV/preview" allow="autoplay"> <iframe src="https://drive.google.com/file/d/1GXZsfN3PoO-WPu_8bhu3jmP11rBmbKBP/preview" width="100%" height="480" allow="autoplay"></iframe></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1RpH7h5Th7upV3gDrJGmXMoIwUztsQAFf/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1A21wyjClFmR5R1Y3BjywvREq0OX-iFex/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1855xR3LLdCSXry_BtjiElU-PlBzndVR1/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1OOlhu6LVXxS7GWw9qsFE1ghKdvBDJsjn/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1vqY6FVbTMaBL2lDVogvpaANsdmHKbn8R/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Alaska Geology Fibrolite Fibrous texture Garnet (Almandine) Growth Zoning Medium- to high-grade metamorphism metamorphic metamorphic rock Porphyroblasts Pre-Kinematic Garnet Pre-tectonic Garnet Prismatic Sillimanite Quartz Inclusions schist Schistosity sillimanite https://bereket-haileab.geology.sites.carleton.edu/files/original/24870104625cd35bdd07121526e63616.jpg 4e2187f2ca83e1185804a235f2192f7e Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-2 Subject The topic of the resource Eclogite Description An account of the resource Major Minerals: garnet, orthopyroxene, clinopyroxene BH250-2 is a high-grade metamorphic rock composed of garnet, orthopyroxene, and clinopyroxene. The pyroxenes exhibit wavy extinction, indicating deformation under ductile conditions. Based on its mineral assemblage, this rock has reached granulite facies, suggesting formation at high temperatures and moderate to high pressures. It likely represents deep crustal rocks that were metamorphosed during continental collision or crustal thickening. Alternatively, due to the dominance of garnet and pyroxenes and the absence of felsic minerals, BH250-2 may also be classified as a garnet pyroxenite, a mafic to ultramafic rock type commonly associated with deep-seated metamorphic or mantle-derived processes. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 2. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=910fe6bf67314fd9ad9b6b1f33241d63" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=1e970aafef764618ba0b8b38815385f3">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/12D_Ye7ovTkKRzfesuF0PJmJV5jQFQTqf/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1k4XXwBTa0_3rm2t1bTggc_aaEoyCvCfS/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1un1hKw1Si67Om3KBy1i7cXDahnZpfJUX/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1T9diGeemH_iEXblM9JjfCQpYANo1iEhA/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Clinopyroxene Garnet Garnet pyroxenite granulite facies High-Grade Metamorphic Rock metamorphic Orthopyroxene Wavy extinction https://bereket-haileab.geology.sites.carleton.edu/files/original/703333991f5bf96ca475d85ee46666a7.jpg f534f6a840f1f7e29eb11c5f8cc2e05f Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-3 Subject The topic of the resource Garnet Mica Schist Description An account of the resource Major Minerals: garnet, muscovite, quartz <br />Minor Minerals: chlorite <br />Click <a href="https://www.digitalscope.org/ViewerUI/?SlideId=7240010f-7c17-472d-9b02-191fd6ae5161">here</a> for a high resolution scan<br /><br /> <p>BH250-3 is a garnet schist, a highly schistose, medium- to high-grade metamorphic rock dominated by garnet and mica. The rock contains euhedral garnets that show signs of retrograde metamorphism, evidenced by the formation of chlorite along the margins and cracks, particularly in the "fish-tail" terminations of the garnets.</p> <p>Notably, the rock also features mica fish—distinctive, lens-shaped or elongate mica crystals aligned within the foliation. These structures are common in deformed metamorphic rocks and serve as indicators of shear sense and strain localization. The presence of both garnet fish and mica fish suggests dynamic metamorphism, with deformation and metamorphic reactions occurring simultaneously.</p> Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-3. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=ad48c50a142b48cd93cddfbafe2abe29" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=3475486a471e46abb795a55c0acb1f83">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1cJgg0c-3xde8skRQOh5zSEoprtnikB4m/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1NeOckZJgIGCQUOV4QKSxrRK_D4RGpf8h/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1nPaE-to0S9SC5jBjMEgDz2g3LFq4RCxk/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Chlorite Chlorite alteration Ductile deformation Euhedral garnet Fish-tail garnet Foliated Metamorphic Rock Garnet Garnet schist Graphite Mica fish Retrograde Metamorphism Schistosity https://bereket-haileab.geology.sites.carleton.edu/files/original/7de3ba7d81c10dfaa6793b3e6ae559db.jpg 11922b1bf4eca370c1785b348f07af50 https://bereket-haileab.geology.sites.carleton.edu/files/original/4496d1bf49afb8bb568304790fc8060d.jpg 9d8a0e708b43c32b05e24dbc354bb214 https://bereket-haileab.geology.sites.carleton.edu/files/original/7826eb6fedeec6673d20cda6b6d5c370.jpeg 1915ddf52e36d1c36734524e72ebf1f3 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-4 Subject The topic of the resource Kyanite Quarzite Description An account of the resource Major Minerals: quartz, kyanite, muscovite, calcite, olivine Minor Minerals: serpentine, rutile Optics: bladed, long prismatic, perfect cleavages, cross parting with 85 degrees BH250-4 is a kyanite quartzite, a high-grade metamorphic rock composed predominantly of quartz and bladed kyanite, with minor amounts of muscovite. The presence of kyanite indicates metamorphism under moderate to high pressure and elevated temperatures, consistent with the kyanite stability field and typical of Barrovian metamorphism. This suggests the rock was buried to mid-crustal depths. The kyanite crystals exhibit a distinct bladed habit, often aligned with the rock’s foliation. The protolith is confidently interpreted as pelitic, originally an aluminum-rich sedimentary rock such as a mudstone or shale, which underwent recrystallization and mineralogical transformation during regional metamorphism. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 4. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Ogilby, California, USA Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=f50d6a62d5a049edbb309cc836017dba" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=f50d6a62d5a049edbb309cc836017dba">here</a><a href="https://carleton.maps.arcgis.com/home/item.html?id=afcac927b670412189fc5bf9a7e9a0e6"></a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1_8Lfa9VIO9JAsf1zsoRVKeiOdGUG-KGT/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1fKJNRyBxAHjSW7RUP6gzMQX0Hsp3pARF/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1YYEiiVy48rH1Vlgl0mIkEBWhy7SSoPgw/preview" allow="autoplay"> <iframe src="https://drive.google.com/file/d/1bo1nzYYoDP4PZMupp-Tz6oXA2dWK9Ek1/preview" width="100%" height="480" allow="autoplay"></iframe></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1bo1nzYYoDP4PZMupp-Tz6oXA2dWK9Ek1/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1cRvZSmxX7pOuX9-UQN6xBYhL97jECPiI/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1J06QEuy4_VaCfcuTwCIKkiIkbdQwl5aE/preview" allow="autoplay"></iframe><br /><br />&lt;iframe width="100%" height="480" Creator An entity primarily responsible for making the resource Bereket Haileab Barrovian metamorphism Bladed kyanite Foliated Metamorphic Rock high-grade metamorphism Kyanite Kyanite quartzite metamorphic metasedimentary muscovite pelitic protolith Quartz quartzite https://bereket-haileab.geology.sites.carleton.edu/files/original/0640d4a5e2982590ca39a8e2802ddc9b.jpg 5105086cf566ba853399a53c0e961503 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-5 Subject The topic of the resource Talc Chlorite Schist Description An account of the resource Major Minerals: talc, chlorite Minor Minerals: calcite BH250-5 is a talc–chlorite schist, a low- to medium-grade metamorphic rock characterized by a strong foliation and a distinctive soapy texture. The dominant minerals are talc and chlorite. Under the microscope, talc exhibits high birefringence, chlorite shows low birefringence, and accessory calcite grains display extremely high birefringence. This sample is excellent for comparing different types of birefringence in minerals under thin section. Calcite occurs as an accessory phase in irregular patches, grains, or veinlets, frequently intergrown with talc and chlorite. The rock is fine- to medium-grained, with minerals aligned perpendicular to the direction of compression, consistent with regional metamorphism. The protolith was likely an ultramafic rock such as serpentinite, the metamorphic assemblage indicates low- to medium-grade conditions, typical of the greenschist facies, possibly influenced by contact metamorphism or talc-carbonation reactions. The formation of chlorite suggests a prolonged retrograde metamorphic overprint, especially related to alteration of mafic minerals. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 5. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=d461c7f1f2984b3fa35a71264357952b" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=d461c7f1f2984b3fa35a71264357952b">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/183H7ea1VwayLj4fVzYVs1mc359vIW_rI/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1OcKG05riOppPmK1RJdR6LA-xCGD3Uq3E/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/186jJQiIFmyUZfcJXkQJI1LkWeG1gN8aN/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1YzA6_1jB_7zc9uEiUXVa3gsPbiZWFMSN/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1kzXVxnbtakR10Iy4qJQy-s1srx24dxF7/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Chlorite Foliated Metamorphic Rock Greenschist facies Low-grade metamorphism mafic protolith Medium-grade metamorphism metamorphic schist Talc Talc–chlorite schist https://bereket-haileab.geology.sites.carleton.edu/files/original/4fb2d5106a4c1074a66327d2efd5a695.jpg 53f6550097155d220a2f257a2eb1e088 https://bereket-haileab.geology.sites.carleton.edu/files/original/1576692a22663335a605cda2e3876ed7.jpg a6dd82dafaffad2050c9277cceff94a8 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Sedimentary Rocks Subject The topic of the resource This collection includes sandstones, limestones, breccias, conglomerates, dolostones, shales, oolites, and BIF. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs. Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-6 Subject The topic of the resource Breccia Description An account of the resource Major Mineral: muscovite, biotite, pyrite, anorthite, quartz Texture Note: evidence of fluids through veins and depositing minerals such as calcite, sulfide BH250-6 is a breccia composed of angular rock fragments containing muscovite, biotite, anorthite and quartz. Numerous veins record the movement of mineral-rich fluids through fractures after brecciation. As the fluids cooled or reacted with the surrounding rock, they deposited calcite and sulfide minerals, including pyrite, along the veins and in open spaces. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 6. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=b1f2a4525fbd4ab699360163f863454f" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=b1f2a4525fbd4ab699360163f863454f">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1CtOmnOIUfJ-TDU040WId32pOQ7-Mf6jl/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1yfgqkafg1xzJ06YUtqiT4uRnt1hlytS6/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AZSDO9ZOf_-TVhIbZBQ__i5xzccH4z4S/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AwftDPmn9Ne82w4oehy1qE_BgdUxbq5Z/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1F54ZU5Tac3AQPAQ30G_zvHJ1fJFxKjFH/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1QLY-7CJyhmwPIRkvS0bGjFHR6SwBPRH-/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab angular fragments breccia fluid flow fracture filling Hydrothermal alteration hydrothermal breccia mineralizing fluids Pyrite sulfide mineralization vein mineralization veins https://bereket-haileab.geology.sites.carleton.edu/files/original/f8d3747c13aa7bffbff8caf6b05d3216.jpg 045d2fb301916955cb0afc850b5fc2d0 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-7 Subject The topic of the resource Garnet Glaucophane Schist Description An account of the resource Major Mineral: glaucophane Minor Minerals: garnet, chlorite Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 7. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=c3ecba37eac84d618b86f88ddfdec655" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=c3ecba37eac84d618b86f88ddfdec655">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1v_vCqy5-pvfBjstp6QWl6TLxGXCZdG6F/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1x3Obs3HGKNtt-j3PJQXs8GPnzzassipm/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1s3nOvnsTx-mhO6I1t1BciTCjE8XNxLfb/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Hh0FjqNqf6vJLLleHHZDGNOB97dxG-PQ/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab metamorphic schist https://bereket-haileab.geology.sites.carleton.edu/files/original/c24e79b749a001892d830bd1dd5d80f2.jpeg 1b4dc3a892d695602334fd93553b6cba Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-8 Subject The topic of the resource Tuff Description An account of the resource Major Mineral: hornblende <br />Minor Mineral: clinopyroxene altering to chlorite, sanidine, titanite, sericite, calcite, apatite<br />Click <a href="https://www.digitalscope.org/ViewerUI/?SlideId=6ebde66b-c6cc-4d73-9f0d-d3b95ab923e9">here</a> for a high resolution scan<br /><br /> <p>BH250-8 is a strikingly beautiful tuff with rich mineralogical features. It contains basaltic hornblende—some crystals showing zoning—as well as both orthopyroxene (OPX) and clinopyroxene (CPX), with some CPX grains displaying anomalous interference colors. Scattered quartz grains are also present. Plagioclase feldspars exhibit alteration to sericite, while portions of the pyroxene have altered to chlorite. Accessory minerals include sphene (titanite) and exceptionally large, well-formed apatite grains—some cut parallel and others perpendicular to the c-axis, clearly revealing basal cleavage. Secondary calcite occurs along veins and voids, and the groundmass contains devitrified and recrystallized volcanic glass. This is a particularly beautiful and mineralogically diverse sample.<br /><br />There are several apatite crystals cut parallel to the C-axis that can be used to determine, length fast, length slow optical property as seeing in the video.</p> Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 8. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=a0a0bd40ee6449d08239c495b3b69bb1" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=a0a0bd40ee6449d08239c495b3b69bb1">here</a><a href="https://carleton.maps.arcgis.com/home/item.html?id=056af387bc7d45bfa762ccd20d45d96b"></a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1l1qnS723ph71--VAF8_tRN7Le8kF1tuk/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1RLGeQ-VcaA7zH_smwNBkhCsStR0373xF/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/16yGJO2oSAeTCLLqrpCFhaXAqKyT2QPiY/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AvJn02wCKcxl5B1SH2pDX0CbCUhdn8jo/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/14ys7YVosrwZHm8btnye6V3icL0Yat75H/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1KFSPbximkQlk4u5dP6npU1vcpwNzmSMz/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1WShR3AY9pJWG9emTk9UJJ9wxRjBoBiUX/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1GIwdoePJw8pxnya8ASrhnBiqGe8H-TgX/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/16QhBGImpt3pfYPi4NncYW_s2_fKJGZC7/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1_MRN8sEFPw-pKXoHYRjRxiI3CV0nQuDy/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1d4vuWNWZ0y9bJ-b8P4odEB8JdYlOekWI/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1jKnVwGcI6KjmDOWoVWQZoJBEEKxN9U7H/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1mk0r0kcv46_RnyQn4f73Y3RdJIokn-TD/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Alteration (sericite Anomalous interference colors Apatite basalt Basaltic hornblende chlorite) Clinopyroxene (CPX) Devitrified Glass Hornblende igneous length fast length slow mafic Orthopyroxene (OPX) Recrystallization Titanite (Sphene) Titanoaugite tuff volcanic volcaniclastic welded tuff Zoned minerals https://bereket-haileab.geology.sites.carleton.edu/files/original/1e4f03f6a59fadb1775f2ca43d8f470a.jpg e16dafeae667600a4a87a17ed46fab94 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-9 Subject The topic of the resource Ortho-pyroxenite Description An account of the resource Major Minerals: orthopyroxene, Minor Minerals: clinopyroxene, olivine, oxides Texture: exsolution lamellae, solid solution between opx and cpx Physical property: 90 degrees cleavage, pyroxene cleavage Petrology: Pyroxenite is an ultramafic, igneous rock composed predominantly of pyroxene minerals, specifically orthopyroxene (opx) and clinopyroxene (cpx), often in nearly equal or varying proportions. In the Webster, North Carolina region, pyroxenites are typically associated with mafic-ultramafic intrusions. These rocks are believed to represent crystallized cumulates from high-temperature mafic magmas or solid residues from partial melting processes in the mantle. BH250-9 is an ortho-pyroxenite with enstatite being the dominant mineral and few olivine, oxides and the exsolved clino-pyrorxene as the makeup of the mineralogy of the rock. Texture: In the pyroxene of BH250-9, exsolution lamellae are common, especially in orthopyroxene, where thin blades of clinopyroxene exsolve due to cooling from high temperature solid solutions. The presence of solid solution between orthopyroxene and clinopyroxene indicates high-temperature equilibrium before exsolution, suggesting that the rock crystallized or equilibrated at elevated pressures and temperatures. Physical and Optical Properties: Cleavage at ~90° is characteristic of pyroxenes (two cleavages intersecting nearly at right angles). The pyroxenes may show parting, exsolution textures, and pleochroism in thin section, aiding in mineral identification. Orthopyroxene is usually brown to green in thin section; clinopyroxene can be colorless to pale green. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-9. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and handsample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=20a9374bea664d20954eab856a70e7f5" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=20a9374bea664d20954eab856a70e7f5">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Zh1ly4CUaS5loy9lXnWm5M-381mXuq-M/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/142OuOFGx65zCRWp1EfYob5qtHsoogr4_/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1H2XDNs6qcVANB9_Io2lYHNgwFCXB7RiZ/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1b6jtQXpVPesqQMyjPguyUtMCrdKw7okS/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/17x5utBrUNk781qozoI_zMk5_c1Y8fT3l/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/17Rny7ew4cja_VfJqswhV3qyVh4mTd8Fc/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AOQijCjgJe3kAP5PG6xmAlH_E9A6ZLMp/preview" allow="autoplay"></iframe> Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Webster, North Carolina, USA Creator An entity primarily responsible for making the resource Bereket Haileab Clinopyroxene Enstatite Exsolution Exsolution lamellae gabbro igneous mafic Mafic-ultramafic intrusion North Carolina Ortho-pyroxenite Orthopyroxene plutonic Pyroxene cleavage (90°) Pyroxene exsolution Pyroxenite cumulate Solid solution Solid solution (opx–cpx) Ultramafic rock Webster https://bereket-haileab.geology.sites.carleton.edu/files/original/767acb0d5f6fe328bbf43e682a2a01c5.jpg ac047440ccee8e066650aa587aeed880 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-10 Subject The topic of the resource Garnet Sillimanite Schist Description An account of the resource Major Minerals: garnet, sillimanite, quartz Minor Mineral: biotite, orthoclase, plagioclase Garnet sillimanite schist is a medium to high-grade metapelitic rock that forms under amphibolite to granulite facies metamorphic conditions. It is derived from aluminous shale or mudstone protoliths and reflects deep crustal metamorphism. In this sample, the major minerals are: Garnet – Large, porphyroblastic, now deformed Sillimanite – Typically occurs as fibrolite or prismatic needles Quartz – Forms the matrix and reflects metamorphic recrystallization Minor minerals: Biotite – Aligned in the foliation, contributes to schistosity Orthoclase and Plagioclase – Present as felsic phases, possibly from original sediment or late-stage metamorphic reaction Microstructure & Deformation: Porphyroblastic garnets are described as prograde and pre-kinematic they grew before the main deformation event and were subsequently deformed, suggesting syn- to post-tectonic strain after garnet crystallization. These garnets now exhibit strain shadows, pressure solution features, or boudinage, indicative of deformation during peak or retrograde metamorphism. Sillimanite are present as fibrolite along foliation planes, reflecting high-temperature metamorphism. Metamorphic Significance: The garnet + sillimanite + quartz ± feldspar assemblage places this rock within the upper amphibolite to granulite facies, and its mineralogy is consistent with pelitic bulk composition. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 10. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=48dc06b1360c410fbc13ced065448ab3" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=48dc06b1360c410fbc13ced065448ab3">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1xcob7AzB2BmD7VBRYqKP1yztLbz7ck-R/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1XYBPoibbVezQiVGHvBrAM4wf_XmpDpcR/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ZyyuLNVzsmzCH-_RtYbu08RfFu6BDlVb/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/19IyP78jbyaG5B4RyOQqmkbQ_12KmaGAf/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1w_fVtBGuqIo3UV1yljMP62b56A2amykz/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1v3rhFuG6aGQTT-8Hzyzn_Ll9w1uwZ7Ns/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1stHfnCglJImTGfPBLBHNM44-OXOSlT6t/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Aluminous protolith Amphibolite Facies Fibrolite Garnet Garnet sillimanite schist granulite facies metamorphic Metapelite porphyroblastic Pre-Kinematic Garnet schist sillimanite https://bereket-haileab.geology.sites.carleton.edu/files/original/721ee5d936a00f317f8a3fe6212eee36.jpg ba5b24e5a7e15a921b99071351b3e2bf Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-11 Subject The topic of the resource Gabbro Description An account of the resource Major Mineral: plagioclase, labradorite, orthopyroxne, clinopyroxene Minor Minerals: olivine, biotite Texture: euhedral plagioclase, anherdral pyroxenes, useful for two competent phase diagrams Optics: optic axis figure on labradorite Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 11. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=607b6049531e4e0d8ec22e53a6d7d4dd" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=607b6049531e4e0d8ec22e53a6d7d4dd">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/16Zgz9-szMKIdWal6wBAZl_taEXAFN-_m/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1UAbOX2xO65mT7Y7wBtnKmyQ464dWnYlO/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1HSCWMXbY5PoY3Au8EC6w1A3ocm4_IWre/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1-G1zsBRxEDBUQbYPI0nAoGspUtL5UO2i/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/188xSQuZV2bWoTcLyCqODV1iII-At78-d/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/145JV5gkNnROLgWBvqjkwcXYooSUqdCvd/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1UrXg2-cT706Cwc8_FcqO9FAJQEAi37cd/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab https://bereket-haileab.geology.sites.carleton.edu/files/original/b00801924613a51d5cffb8e92b81b73e.jpg bd80ff0163bea00b301c010822a77a0d Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-12 Subject The topic of the resource Fluorite Vein Description An account of the resource Major Minerals: calcite, fluorite, aegirine, quartz, olivine Minor Mineral: serpentine Mineralogy Comments: fluorite has purple spots Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Alta, Utah, USA Nearby Geographic Features: Alta Stock Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 12. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=043cd8b0846749b5bdb22fb8177cf1d7" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=043cd8b0846749b5bdb22fb8177cf1d7">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1QxKjNqLO19YzrZApstg9h2KIllzy9H2z/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1A4diE1P-ilug-A6y0yX2BoJ-mZ8ykw-2/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1bajVnZLfnY-7gTJq1pKMxmFByUHjPRJk/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1JcXHTSzcwMdSAgTnqvK-y2WwQs6yvxWd/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/151ZBZgrb8pqTr0X6RV4GzhtQ0IjbO4V6/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab hydrothermal https://bereket-haileab.geology.sites.carleton.edu/files/original/a47993b62ab904a6c4beca006b93f841.jpg fcb3f61f2fc5b27316eeebd3d128e8a4 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-12b Subject The topic of the resource Fluorite Vein Description An account of the resource Major Minerals: fluorite Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 12b. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=f215c3bf58b947da88acb46ac875e936" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=f215c3bf58b947da88acb46ac875e936">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hoNknFbeBeuzVireyuW4L2vRhmijbdTU/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1z3XXodClMMDroegzUiad4QTa-j2rIpQl/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab hydrothermal https://bereket-haileab.geology.sites.carleton.edu/files/original/3ca30622751c40964226d88303ce386c.jpeg 55bc810c63e9df93b6f7fe1f11d37cfe Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-13 Subject The topic of the resource Granite Description An account of the resource Major Minerals: quartz, orthoclase, albite Minor Minerals: hornblende, titanite (sphene), zircon, biotite, microcline, perthite, sericite, chlorite, calcite (secondary), apatite Mineralogy Comments: myrmekite Optics: small 2V, biotite BXA(x) figure, optically negative biaxial mineral, biotite cut perpendicular to c-axis, radiation damage, pleochroic halo, tar tarn twining Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-13. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=38b32e0ac84f4f36a530c2a339a45589" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=38ea461ce7b74f068953c9d1ee42644c">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1cJI7zDZY1RtFYwnCvcskmUgq0UhXe1-v/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1IBGmc5XPJtFUdNPmfdonlh3z8SRAedi8/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/176KRF0_7WHLKpEBIy9Daeg3DrO8xjtdl/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1OgGj5utm683ODh0HBzxrb0-IE0pYCG7T/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1BtSJxKEZLVwTC9-SEreOowOhiMwbIx0U/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/161xK1tlJn7GbJwwfVZrxLZhoHK7kDzNn/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Tj_dyB4yAnos0tGTvYUpa2pReIi3wPX8/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1-yEkjWsGsZVEx-ijk7tJepkWY4w__cgD/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1_JVcNKe6N8pNu-JQVnQzOg9sW4-RgYUi/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1fbWntjGx7-Vi9OqkZbhvGr9NgHy6hwog/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ud1Ri0jIdfPg04odQwY3fCJ5euxU-uuv/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/19mDY_envJ5WlLSIC3tNE-XrmLN0F7YV4/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab felsic granite igneous plutonic https://bereket-haileab.geology.sites.carleton.edu/files/original/c0da0ddb890438ece780445db47357e5.jpeg 1b25ee2177c3e02b04452c89e5547a57 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-14 Subject The topic of the resource Mica Schist Description An account of the resource Major Minerals: quartz, bytownite, biotite, muscovite Mineralogy Comments: biotite interwoven with muscovite Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-14. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=571df879477548e3b893eb5c32f09f09" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=38ea461ce7b74f068953c9d1ee42644c">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1dNF1XqrRpKRrVbAFk51rNXUqRTS7Yicu/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/16hADCMubi72VY-_M4H23fJF9a3gKeSxD/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Oijg3gmXTeo-axg6Sh813RBOwVXaYRfb/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1CX8JGpgJDM6TyD6ePtepJlBoQMBCYVaj/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1OGDiSxKzEEPi5SjbBfolBl4HJ4pjaQSs/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1jOajftw2vwLyseeziMF5WayrzrelOGr5/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1g7UAd3wbfd4dbsBX2V-YlwaqBMn_25zS/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab metamorphic schist https://bereket-haileab.geology.sites.carleton.edu/files/original/da98f6b873d85c5ec3a25358375f1225.jpeg df8533def48341d8a24862a55165e7b2 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-15 Subject The topic of the resource Andesite, true andesite Description An account of the resource Major Minerals: amphibole, plagioclase <br />Minor Mineral: glass <br />Texture: amphibole dehydration, trachytic flow<br /><br /> <p>BH250-15b is an andesite from Mt. Shasta, California. When plotted on the TAS (Total Alkali–Silica) diagram, it falls within the dacite field, indicating a slightly more evolved composition than typical andesite. Twinned amphiboles and plagioclase feldspar are common. Its mineralogy includes phenocrysts of hornblende and plagioclase feldspar. The matrix consists of fine-grained feldspar and volcanic glass. Both phenocryst types exhibit zoning, suggesting changes in magmatic conditions during crystallization. The hornblende phenocrysts display dehydration reaction rims, with the extent of alteration ranging from thin margins to rims so extensive that they have nearly consumed the amphibole entirely.<br /><br /></p> <p><span style="color: black;">In this sample, you can observe<span class="apple-converted-space">&nbsp;</span><strong data-start="120" data-end="146"><span style="font-weight: normal;">hornblende dehydration</span></strong><b>,</b> a key mineral reaction that records changing magma conditions during ascent. Hornblende is a hydrous amphibole, stable only at relatively high pressure and in water-rich magmas. As magma rises, pressure decreases and dissolved water exsolves, destabilizing hornblende. It then breaks down into minerals stable under drier, lower-pressure conditions, typically forming pyroxene, plagioclase, and iron oxides such as magnetite, while releasing water vapor.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="604" data-end="1212"><span style="color: black;">This process commonly produces<span class="apple-converted-space">&nbsp;</span><strong data-start="635" data-end="652"><span style="font-weight: normal;">reaction rims</span></strong><span class="apple-converted-space">&nbsp;</span>around hornblende crystals. These dark, opaque “opacite rims” consist of very fine-grained oxides and pyroxenes and indicate that the dehydration reaction began but did not go to completion, usually due to relatively rapid magma ascent. In contrast, complete alteration occurs when hornblende is entirely replaced by these secondary minerals, preserving only the original crystal shape as a<span class="apple-converted-space">&nbsp;</span><strong data-start="1044" data-end="1059"><span style="font-weight: normal;">pseudomorph</span></strong>. In some cases, the breakdown products may also include minor glass or extremely fine-grained intergrowths, reflecting rapid quenching near the surface.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="1214" data-end="1671"><span style="color: black;">The thickness and development of these rims provide important clues about magma dynamics. Thin rims suggest rapid ascent and limited time for reaction, whereas thick rims or complete replacement indicate slower ascent, longer residence at shallow depth, or more extensive degassing prior to eruption. These textures are therefore considered classic<span class="apple-converted-space">&nbsp;</span><strong data-start="1563" data-end="1590"><span style="font-weight: normal;">disequilibrium features</span></strong>, showing that minerals did not have time to fully adjust to changing conditions.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="1673" data-end="2187"><strong data-start="1673" data-end="1821"><span style="color: black; font-weight: normal;">Compared to BH250-15b and BH250-120, where most of the hornblende is completely dehydrated and replaced, this sample preserves earlier stages of the reaction.</span></strong><span class="apple-converted-space"><span style="color: black;">&nbsp;</span></span><span style="color: black;">The presence of partial reaction rims here suggests that magma ascent was faster or that the crystals experienced less time under low-pressure, degassing conditions. In contrast, the more complete dehydration observed in BH250-120 indicates longer residence at shallow depths or more extensive pre-eruptive degassing, allowing the reaction to proceed to completion.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="2189" data-end="2640" data-is-last-node="" data-is-only-node=""><span style="color: black;">Overall, hornblende dehydration textures are powerful indicators of magma evolution. Because hornblende stability is strongly tied to water content, its breakdown provides direct evidence of<span class="apple-converted-space">&nbsp;</span><strong data-start="2380" data-end="2424"><span style="font-weight: normal;">pre-eruptive degassing and decompression</span></strong><span class="apple-converted-space">&nbsp;</span>in volcanic systems. These features are especially common in intermediate magmas such as andesite and dacite and are widely used to interpret ascent rates, storage conditions, and eruption dynamics in volcanic arcs.</span></p> <br /><br />Optics: pleochroism in amphibole, Carlsbad twining Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-15. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=87cb287111644d20a3e727d83a795ebd" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <a href="&lt;iframe src=&quot;https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=87cb287111644d20a3e727d83a795ebd&quot; width=&quot;400&quot; height=&quot;600&quot; frameborder=&quot;0&quot; style=&quot;border:0&quot; allowfullscreen&gt;iFrames are not supported on this page.&lt;/iframe&gt;"></a><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=1556b48fc03540b8ada472f0d3898607">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1PH1WZBRbYyGwWIIVKjTXjty3EuuyPYZv/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/15C51AErjn3uuvHFr43n4LlT_sE05W3TY/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1liRBBlmDfx2Kz1O2zH_6RdDuKVrktIGP/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1lECGx-VS8E82aLsboB-AlvPzttCZvYIV/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1wRtiI5ouH9z13twFZvMcKVCOGC4onQ_G/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1akJjToYhi_k7g7O05-WDpl7yyvpin-Rv/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1O1wubeYi99yo0HLadOHFCF5X0B8hqCme/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1691cxuMO9uSKM-OkM45r7EA0t7f8j2Ad/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1g3MpeQE7MgLR5Ao86WOhdWySOmXA0pFn/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/15YS5CGEvCiUWUzhNzO4Hv9A0PCEa6Lw9/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1olveWFKtwgPe4XEhcmEwVZvMoA_cGk_N/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1QGSnmx5dbGrd-sDD9tnz5kdZB11Qqzw7/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/12KSdFWvzb1j86AQDcCylAtr4zILSriR_/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1KAWsU-CLwiFFVNvaohn9IQ5ePgGwqT5P/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab andesite dacite Dehydration reaction in amphiboles Dehydration Rim felsic Hornblende igneous intermediate Mt Shasta phenocryst Plagioclase TagsAmphibole Alteration TAS diagram Total Alkali–Silica diagram volcanic Volcanic glass Zoning https://bereket-haileab.geology.sites.carleton.edu/files/original/3c96c75955f18fe1d92798a0aff66b28.jpg de96be70c9934138a0e34f88d96dc416 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-15b Subject The topic of the resource Andesite Description An account of the resource Major Minerals: amphibole, plagioclase<br />Minor minerals: glass<br />Texture: trachytic flow, dehydration rim on amphibole<br /><br /> <p>BH250-15b is an andesite from Mt. Shasta, California. When plotted on the TAS (Total Alkali–Silica) diagram, it falls within the dacite field, indicating a slightly more evolved composition than typical andesite. Twinned amphiboles and plagioclase feldspar are common. Its mineralogy includes phenocrysts of hornblende and plagioclase feldspar. The matrix consists of fine-grained feldspar and volcanic glass. Both phenocryst types exhibit zoning, suggesting changes in magmatic conditions during crystallization. The hornblende phenocrysts display dehydration reaction rims, with the extent of alteration ranging from thin margins to rims so extensive that they have nearly consumed the amphibole entirely.<br /><br /></p> <p><span style="color: black;">In this sample, you can observe<span class="apple-converted-space">&nbsp;</span><strong data-start="120" data-end="146"><span style="font-weight: normal;">hornblende dehydration</span></strong><b>,</b> a key mineral reaction that records changing magma conditions during ascent. Hornblende is a hydrous amphibole, stable only at relatively high pressure and in water-rich magmas. As magma rises, pressure decreases and dissolved water exsolves, destabilizing hornblende. It then breaks down into minerals stable under drier, lower-pressure conditions, typically forming pyroxene, plagioclase, and iron oxides such as magnetite, while releasing water vapor.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="604" data-end="1212"><span style="color: black;">This process commonly produces<span class="apple-converted-space">&nbsp;</span><strong data-start="635" data-end="652"><span style="font-weight: normal;">reaction rims</span></strong><span class="apple-converted-space">&nbsp;</span>around hornblende crystals. These dark, opaque “opacite rims” consist of very fine-grained oxides and pyroxenes and indicate that the dehydration reaction began but did not go to completion, usually due to relatively rapid magma ascent. In contrast, complete alteration occurs when hornblende is entirely replaced by these secondary minerals, preserving only the original crystal shape as a<span class="apple-converted-space">&nbsp;</span><strong data-start="1044" data-end="1059"><span style="font-weight: normal;">pseudomorph</span></strong>. In some cases, the breakdown products may also include minor glass or extremely fine-grained intergrowths, reflecting rapid quenching near the surface.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="1214" data-end="1671"><span style="color: black;">The thickness and development of these rims provide important clues about magma dynamics. Thin rims suggest rapid ascent and limited time for reaction, whereas thick rims or complete replacement indicate slower ascent, longer residence at shallow depth, or more extensive degassing prior to eruption. These textures are therefore considered classic<span class="apple-converted-space">&nbsp;</span><strong data-start="1563" data-end="1590"><span style="font-weight: normal;">disequilibrium features</span></strong>, showing that minerals did not have time to fully adjust to changing conditions.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="1673" data-end="2187"><strong data-start="1673" data-end="1821"><span style="color: black; font-weight: normal;">Compared to BH250-120, where most of the hornblende is completely dehydrated and replaced, this sample preserves earlier stages of the reaction.</span></strong><span class="apple-converted-space"><span style="color: black;">&nbsp;</span></span><span style="color: black;">The presence of partial reaction rims here suggests that magma ascent was faster or that the crystals experienced less time under low-pressure, degassing conditions. In contrast, the more complete dehydration observed in BH250-120 indicates longer residence at shallow depths or more extensive pre-eruptive degassing, allowing the reaction to proceed to completion.<o:p></o:p></span></p> <p style="caret-color: #000000; font-variant-caps: normal; orphans: auto; text-align: start; widows: auto; -webkit-text-stroke-width: 0px; word-spacing: 0px;" data-start="2189" data-end="2640" data-is-last-node="" data-is-only-node=""><span style="color: black;">Overall, hornblende dehydration textures are powerful indicators of magma evolution. Because hornblende stability is strongly tied to water content, its breakdown provides direct evidence of<span class="apple-converted-space">&nbsp;</span><strong data-start="2380" data-end="2424"><span style="font-weight: normal;">pre-eruptive degassing and decompression</span></strong><span class="apple-converted-space">&nbsp;</span>in volcanic systems. These features are especially common in intermediate magmas such as andesite and dacite and are widely used to interpret ascent rates, storage conditions, and eruption dynamics in volcanic arcs.<o:p></o:p></span></p> <br /><iframe width="1800" height="100" src="https://docs.google.com/spreadsheets/d/e/2PACX-1vS4nyqCmZQGn3t6vX4g4nhDPwHMBaKrigt1LaY2pykWbBGXB1wNb6FYArx625I-JTtD7lyg4uz1OS1r/pubhtml?gid=1910588120&amp;single=true&amp;widget=true&amp;headers=false"></iframe> Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Mt. Shasta, California, USA Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 15b. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=0189377d17504a34af71bbc3099602e3" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> &nbsp;<br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=5075f33fcb6249a8b7b0a98e47f54791">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1C3mZOUJ5jOAUOvXLHzSbT-crRyiVkXoA/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1FK_Oxli2AxlauCyOWTznGoaod_zwhwS1/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1WjZI8mUuWnB4aeUPj6VHFeTI-qCtSJKT/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1n5jZoCjYCUWhw3VwrZRxOJEP0F1FOiwN/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/18RJUQNSKqlA2s7mh-X6MVb-6o0ghct06/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1EiBtxs6sCFJeHMG8R6AYyAwBdZTK8D-d/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1O9OB8JmpXWsj6EYy59THjjO_EGPfaP0v/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1o8rbSoUyDTC709WpJh4VeAOkYmM9XI2L/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1HkAZJEbA4SnnOMC9l4-ah4Y1_9lR3Ysv/preview" allow="autoplay"></iframe> TAS diagram for sample 15b. Creator An entity primarily responsible for making the resource Bereket Haileab Amphibole Alteration andesite dacite Dehydration reaction in amphiboles Dehydration Rim felsic Hornblende igneous Mt Shasta phenocryst Plagioclase TAS diagram Total Alkali–Silica diagram volcanic Volcanic glass Zoning https://bereket-haileab.geology.sites.carleton.edu/files/original/20774fd1684e8c4f9fe3d05f7e6044a3.jpg 4745151a71ea8615af7d216527bffe60 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-16 Subject The topic of the resource Phonolite Description An account of the resource Major Minerals: orthoclase, nepheline, aegirine-augite, albite, cordierite Minor Minerals: titanite (sphene), biotite, hornblende, apatite, anthophyllite, muscovite Mineralogy Comments: hornblende euhedral Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 16. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=365d00f450f341de99126330d3a3d933" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=365d00f450f341de99126330d3a3d933">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1HHOXXvtn2W8-Dq9yVlW8Gfn-y8QKBgjq/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1A07cRQZc94JIfRSIG3kEXW5-P31eNxvA/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1xj908k9MxxtiXlqQke311LEKqzxQUq_3/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1pyX4g15BA80YCZugTzrSmQ5lI9c4sfTt/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1vE8hFzm0dXAEEVnD8D75Esty63WSihKt/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1PFz8usQYGHEHkmRMgeJnUzYUu04eGVBF/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1lKcrHVKpKn4Xhlo-K6PUdpOFVoJBhxYI/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1NX0Z1bbTuzOgKD6jZ8lfXSwkN6CWjaDz/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Fl3oWoPb7sWYish4XxGtcFy2mMibCS4c/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab igneous intermediate phonolite volcanic https://bereket-haileab.geology.sites.carleton.edu/files/original/73298495cf39fd0c53c08214852851a9.jpg 416310617c73dca607bc2bbbe78823ef Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-17 Subject The topic of the resource Dunite Description An account of the resource Major Mineral: olivine Minor Minerals: clinopyroxene, magnetite, serpentine Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 17. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=a8b5ce98f4754c96a108e7e7e56d416a" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=a8b5ce98f4754c96a108e7e7e56d416a">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Q79K2qLhYzXO56VtEMe7WQuystwzF9WA/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/152DZ_0fV7RdJPJXY6Qum9PRg7YkcShUj/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1XJ2zctadXHWYX7okQ4B1brDBl0hm95Zy/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab dunite igneous plutonic ultramafic https://bereket-haileab.geology.sites.carleton.edu/files/original/81c6d8869ccd2da5b29d9329fca79c87.jpg 9e651feda16146822eb27b4ddebb0d8e Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-18 Subject The topic of the resource Cordierite anthophyllite skarn Description An account of the resource Major Minerals: cordierite, anthophyllite, spinel, augite, melilite, biotite Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Guffey, Colorado, USA Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 18. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=9400838c180e4f1a9300f0be92185435" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=9400838c180e4f1a9300f0be92185435">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1jj8cH-c7Xma_MA_o96zZn8P_Bh4imm9g/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/10ETjCFk5-dFjPC32d5LgLA37QeFqEZd0/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/17WLtNGPrrbfOhLKcRxnDAYMdL1yCebyc/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/10JHCwFtfJBBSg-CNOz0qJDkDPOF2DxE3/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1NrBgidZ6A-a5eD9wJjYwUW_MLgIztRZI/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1wz3NebhJlbRy_f5z-Y410CgqVYMP4L_k/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1KSgqTVOreYzLgGZny2O45WvGqdzk_USV/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1UJGAaKTwFSARoc82bv8Qc62RKyI2ViEf/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1xVv6nEseCxn1ql45_uhm1g8AlgXu363i/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/14Gse0Mj_4CfmtRB6tkhrHNDTYOR_pIyB/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/15OibGyeRpCqkzbAVc2zwRtSzWvbl7ksu/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hejMLf_2-dJahlEZ0unvy9COzUV8LNPm/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1N-U7K5wAK8IdUMplLmuLN8u18vgM5cqZ/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab metamorphic metasomatic skarn https://bereket-haileab.geology.sites.carleton.edu/files/original/48fafb17db021c0262ea002c2b627d54.jpg b153d7c4311544dd9e5b68bcc65f60c1 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-18b Subject The topic of the resource Gabbro Description An account of the resource Major Minerals: spinel, clinopyroxene, olivine Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Utah, USA Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 18b. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Creator An entity primarily responsible for making the resource Bereket Haileab Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=202f09ae437c48f0805a0acbbc501abb" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=91cdd9d370a849f081326e76ad8796b4">here</a> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ejdZ0_ZfRz3S4NF2V41I7P9P8I9Z4rIv/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1viMl6U2yO3m-8-e9ZMhQmAWrClocvDDW/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1A5FvtbibXRd4V6MnaXlmoFSEOnuKikWh/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1sTWfUScdPxK9AJ2EtplHRYeMZJGV_6f5/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1fAuLcV61OmR_VR7shHmXb6vXooRwRJZw/preview" allow="autoplay"></iframe> <br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1kiNuSoHTjLxNb-gfgjfDtz5y4WMgOkav/preview" allow="autoplay"></iframe> gabbro igneous mafic plutonic https://bereket-haileab.geology.sites.carleton.edu/files/original/af3fbe720df930760777da7ef6da35e8.jpg 1173545ed8f4e4cb60d9a76190786b69 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-19 Subject The topic of the resource Tuff, Welded tuff, Ignimbrite Description An account of the resource Major Minerals: quartz, albite, biotite, sanidine, glass, basaltic hornblende, clinopyroxene, augite<br />Mineralogy Comment: biotite shows kink band, possibly deformation during flow; perfect cleavage is visible in the biotite, zoning&nbsp;<br /><br /> <p>BH250-19 is a welded tuff containing phenocrysts of basaltic hornblende, biotite, clinopyroxene, orthopyroxene, and quartz. The matrix is composed of devitrified volcanic glass, preserving the texture typical of welded pyroclastic deposits. This thin section is an excellent teaching example for identifying welded tuff textures, recognizing phenocrysts, and distinguishing between biotite and hornblende under the microscope. Evidence of brecciation is also present, giving the rock characteristics of a volcanic breccia. When plotted on the TAS (Total Alkali–Silica) diagram, the bulk composition falls at the boundary between andesite and trachyandesite, reflecting a transitional composition in the volcanic series.</p> <br /><br /><iframe width="1800" height="100" src="https://docs.google.com/spreadsheets/d/e/2PACX-1vS4nyqCmZQGn3t6vX4g4nhDPwHMBaKrigt1LaY2pykWbBGXB1wNb6FYArx625I-JTtD7lyg4uz1OS1r/pubhtml?gid=1158317021&amp;single=true&amp;widget=true&amp;headers=false"></iframe> Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 19. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=51a58c15b64f46f69a6de7b2174a919d" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=51a58c15b64f46f69a6de7b2174a919d">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1d0agziKHCM3w3h7-Jq-oJsJijDBYUk-a/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AJ3C1I9ipurdxMUJcD4BetxMOXGy16jG/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1u3ffFLpp4LagAHmDSlECXTTgYG8Obl2B/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1lgfrtESBOS_0j9uT1wgFfzg6Z9VxBHlr/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1YRoG_Dopm5GXd-ogF1MHgPzc25EZhYJR/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1n3TjSnoAH9fyuTnpjmHM_oQVgzXeCYEK/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1EtKaShXXEc4s8iPQFQ6NpyL1qf6niosV/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1JwXoszulF7k4mnoYpbCrRToCf2eJ4oA2/preview" allow="autoplay"><iframe src="https://drive.google.com/file/d/1fZSwqrXdc4TzsfFB3qG-Qzsae2xGMLje/preview" width="100%" height="480" allow="autoplay"></iframe></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1G8kJObVOdTxhQn45xPnS5GgYKokTkN-Q/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1NFC5NmX702TjHp5vv5MePicRYF4hl-ep/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1gq_9fFEaFAfZqjB7qBS_UgD2NfaWfqkN/preview" allow="autoplay"></iframe><br />TAS diagram of sample BH250-19. Creator An entity primarily responsible for making the resource Bereket Haileab andesite Basaltic hornblende Biotite Brecciation Clinopyroxene Devitrified Glass Hornblende Orthopyroxene phenocryst Quartz sedimentary TAS diagram Total Alkali Silica diagram Trachyandesite tuff volcanic Volcanic Breccia volcaniclastic welded tuff https://bereket-haileab.geology.sites.carleton.edu/files/original/ef9b1d9b2b2e1c1acbff17c08a8e833b.jpg fc54e4ac5393db0ea820b1b8a30ba2bc Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-20 Subject The topic of the resource Garnet Staurolite Mica Schist Description An account of the resource Major Mineral: garnet, staurolite, biotite, muscovite, quartz Minor Mineral: graphite Texture: foliation around staurolite, inclusion in staurolite Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-20. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=d633edbd8c9f4b0dadff578e0c860781" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=d633edbd8c9f4b0dadff578e0c860781">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1UhM_pyuRTeD8ZO3nF5PMn-JKj_u1PsN0/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1r-yEep-UkAkQeuBYj-p8YCuKpTgZPaBj/preview" allow="autoplay"></iframe>&nbsp;<br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Go6YEgh2oZOAoTJFbkuugJkBTe9APiR7/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1JYrpTgHn6LmejvXBqgTFHBmR4702a3to/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ZaIObatiephEque4mmRIHlzWkZ6n37xM/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab metamorphic schist https://bereket-haileab.geology.sites.carleton.edu/files/original/5862a6b79a428df66087a36c1c2a07fe.jpg adab2691159d117552acd92136c762da Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-21 Subject The topic of the resource Quartzite/ Mylonite Description An account of the resource Major Mineral: quartz Minor Mineral: muscovite Mineralogy Comments: the quartz grains are deformed and show lineation Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-21. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=981eaf28467d428396ca300e4e481e0b" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=981eaf28467d428396ca300e4e481e0b">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/13M8o6R7WFHTVqQpfByetkTFNuvxy345_/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1yrRs6NdNUsGtjiwkvAU5XdaePZsnGWZA/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Q8jYZDgjWodtQtSG0jEBz1dqgekvnSZe/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ffdjKMOXuHlbUT0mmLJSEmffYtNntpSR/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab metamorphic metasedimentary quartzite https://bereket-haileab.geology.sites.carleton.edu/files/original/87ad17e92de78cab49a6aa8d91882cd9.jpg bc997fe04cb404f8c5b9d523a78ef25f Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-22 Subject The topic of the resource Chloritoid Schist Description An account of the resource <p class="isSelectedEnd"><strong><span>Major Mineral:</span></strong><span> Chloritoid<br />Minor minerals: Garnet, quartz, muscovite, and graphite<br /></span></p> <p class="isSelectedEnd"><span>BH250-22 is an excellent example of a strongly foliated metamorphic rock that records a prolonged and complex history of deformation and metamorphism. The rock is characterized by a well-developed schistosity defined primarily by aligned muscovite and graphite, making it one of the most strongly foliated specimens among related samples. Its mineral assemblage and microstructures preserve evidence for multiple episodes of mineral growth, deformation, and recrystallization, providing valuable insight into the tectonic evolution of the metamorphic terrane from which it was collected.</span></p> <p class="isSelectedEnd"><span>The dominant mineral of the rock is chloritoid, an important index mineral that occurs as both pre-kinematic and syn-kinematic porphyroblasts. The presence of chloritoid crystals that contain internal foliation demonstrates that some grains grew after an earlier fabric had already formed, while other crystals continued to grow during deformation. This relationship provides strong evidence for progressive metamorphism accompanied by multiple phases of deformation. Garnet is also present as porphyroblasts and commonly contains inclusion trails that preserve earlier foliation patterns within the crystals. These internal structures offer a record of changing metamorphic conditions and deformation histories during crystal growth.</span></p> <p class="isSelectedEnd"><span>Quartz forms an important component of the rock matrix and commonly displays undulatory extinction, indicating deformation under elevated temperatures. Pressure shadows adjacent to garnet and chloritoid porphyroblasts further attest to significant strain during metamorphism. In some areas, quartz appears concentrated into thin compositional layers or segregations parallel to foliation. Muscovite is abundant and largely responsible for the rock's pronounced schistosity, while graphite occurs as fine opaque material aligned along cleavage planes and foliation surfaces, enhancing the planar fabric.</span></p> <p class="isSelectedEnd"><span>Microscopic examination reveals a variety of textures that document the rock's complex evolution. The foliation is exceptionally well developed and defined by the preferred orientation of muscovite and graphite. Garnet and chloritoid are the principal porphyroblastic minerals, and many chloritoid crystals preserve internal foliations that differ from the external foliation of the matrix. These relationships indicate that mineral growth and deformation were not separate events but instead overlapped through time. The coexistence of pre-kinematic and syn-kinematic garnet and chloritoid demonstrates that metamorphism occurred during progressive deformation, with mineral growth continuing through successive tectonic events.</span></p> <p class="isSelectedEnd"><span>Evidence of later brittle deformation is also preserved within the rock. Some mica-rich domains, particularly those associated with chloritoid-bearing areas, exhibit fractures and other brittle features that likely developed during a later stage of tectonic activity when temperatures had declined. These late structures overprint earlier ductile fabrics and record the final stages of the rock's tectonic history.</span></p> <p class="isSelectedEnd"><span>The mineral assemblage of chloritoid, garnet, quartz, muscovite, and graphite suggests metamorphic conditions within the greenschist to lower amphibolite facies range, corresponding to moderate temperatures and intermediate pressures. Such conditions are typical of regional metamorphism associated with mountain-building processes. The textural relationships preserved in BH250-22 indicate that metamorphism and deformation occurred progressively rather than during a single event, reflecting a dynamic tectonic environment characterized by repeated pulses of stress, recrystallization, and mineral growth.</span></p> <p class="isSelectedEnd"><span>The geological significance of BH250-22 extends beyond the specimen itself because it provides insight into the tectonic history of Eritrea and the surrounding East African region. Much of Eritrea's crystalline basement consists of Neoproterozoic metamorphic rocks that formed during the East African Orogeny, approximately 850–550 million years ago. This major tectonic event culminated in the assembly of the Arabian-Nubian Shield and played a key role in the formation of Gondwana. Schists, gneisses, amphibolites, and related metamorphic rocks throughout Eritrea were subjected to regional metamorphism and deformation during this period.</span></p> <p><span>The most significant tectono-metamorphic episode was the Pan-African Orogeny, approximately 650–550 million years ago, when continental fragments collided and were welded together during the final assembly of Gondwana. Many of Eritrea's metamorphic rocks either formed or were extensively reworked during this event. BH250-22 likely records part of this prolonged history of mountain building, metamorphism, and deformation, preserving in its minerals and textures a record of the tectonic processes that shaped northeastern Africa during the late Neoproterozoic.</span></p> <br /><br />Click <a href="https://www.digitalscope.org/ViewerUI/?SlideId=6455a78f-f4ff-4f92-a99d-3906122c2e55">here</a> for a high resolution scan by digitalscope Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-22. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=23e6331d72f14352aaa78f9fb81b54bd" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=23e6331d72f14352aaa78f9fb81b54bd">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1pQhfioq6nCiYXdyZtcn8xfSZlAMMjCeN/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AGHzuvrOVb1OrwHlM6DU4U2XV7hRL_o5/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1FgjwHkzVW4lVdJSMAhvnW4rU8FqjpGIr/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1v_GyKpyDiw-YQdT0dwrhXHisesWqGQBw/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/145PIHFO5Fj4gIKbVZLym6hHF4zXCYJVG/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1U5G2IogcJfYnCnxWzmOFqoM7kZVPX5Lp/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1zhdaAXSvoMRoBqzZa_2eUSUPLTci1IJm/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ukuH6HxpU2Fg0w86-RolAr8tFUg5NDMR/preview" allow="autoplay"></iframe> Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Chloridoid schist collected from Eritrea. Few kilometers north of the city of Keren. Approximate location, 15°53'38.62"N, 38°26'58.59"E. Date A point or period of time associated with an event in the lifecycle of the resource Summer 1996, field trip with Professor Paul Retain of Buffalo University, NY Creator An entity primarily responsible for making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab Arabian-Nubian Shield Brittle mica Chloritoid Chloritoid schist Chloritoid-Garnet-Mica Schist Continental Collision Digital Microscope Scan East African Orogeny Eritrea Foliated Metamorphic Rock Foliation Garnet Graphite Keren Eritrea metamorphic Micaceous Texture Multi-stadial growth Neoproterozoic Pan-African Orogeny Porphyroblast Porphyroblastic texture Porphyroblasts Pre-kinematic chloritoid schist Schistosity Strong Foliation Syn-kinematic chloritoid https://bereket-haileab.geology.sites.carleton.edu/files/original/c5e9583f7c5f8235b6b725ed1f0b9bd9.jpg 4881f523ca2e3efb7e5cc4bf9152ee27 https://bereket-haileab.geology.sites.carleton.edu/files/original/022ca1d0ae122b2aa3fda62ce44818f3.jpg 40c74708c731caa158fd784effce0447 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-23 Subject The topic of the resource Glaucophane Schist Description An account of the resource Major Mineral: Glaucophane Description BH250-23 is a fine-grained, foliated metamorphic rock characterized by a blue to lavender hue due to its high content of glaucophane, a sodic amphibole that forms under high-pressure, low-temperature conditions typical of blueschist facies metamorphism. This rock is a textbook example of subduction zone metamorphism. Mineralogy: Glaucophane is the dominant mineral; occurs as euhedral to subhedral crystals with distinctive blue to lavender pleochroism. It is a sodic amphibole, and its presence marks high-pressure conditions. Na-bearing amphibole: General term likely referring to the compositional variety among amphiboles that includes glaucophane. Quartz: Present in the matrix, contributing to the rock’s overall strength and interlocking texture. Texture: Radiating glaucophane crystals: Glaucophane forms acicular to prismatic crystals that radiate from growth centers, giving a characteristic texture. Porphyroblastic texture: Some glaucophane crystals may grow larger than the matrix, forming porphyroblasts. Foliation: Defined by alignment of elongated glaucophane crystals and quartz ribbons. Optical Properties: Pleochroism: Glaucophane displays strong pleochroism, typically: Cleavage: Perfect in two directions at 60° and 120°, typical of amphiboles. Accouple of movies that show this cleavage sets are available. Glaucophane schist belongs to the blueschist facies, diagnostic of subduction zones where oceanic crust and sediments are buried rapidly and metamorphosed under high pressure, low temperature. Common in accretionary prisms and subduction complexes. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-23. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=a250d97d21ac4c59b2ef236b64b1f1b6" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=0898792913244ee3acd60b95cd12ef73">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1oMuQ1UMbQbrU97t_hJMdv5IJRCFUnDSK/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/19e9DfdMtXAtJgNxR9HNkwyNS8XOMFO3H/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1kgfppBz2pqALtjPSUXJS3Bto0HJ9Xe1K/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1nv_k3RhI3GDzQiSIZWhpkl0zTIFl9vTh/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/11TUB1YjBabobyjadWFQ40ZyQREPYB4JA/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1f0wxV540uVssHRNM1J3hTl8xREUIUFhc/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/15gYb69X203XWiTy_LCkozBW9no6Aw7O2/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AHG1tiqdp1dyEBBq2xm5DUxR_f9MXmGH/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/15KIlviv5-3hBpfFWW9n3o4gm26RSMtnE/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/19EkOcyQulOZwVbs9MmIWLbFFCYL1-pn1/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/13NVpiqvheZVAUdR8Ib2heWlv4BOE7MCu/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1642jaeohSZ3fh9V6tDCytf1AI1OpiHfL/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1p66rcSvoBKIM12dmMddga700S4o1gumg/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1d-5rUjlQMB9n-5YLk1z46oY-RA42OWSo/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/1dZV0NTf_eeK1CY_jna_Aay4w4mD7Rvam/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/137hVStNOTEVRBKThdTyDStkDbFN6rrjm/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Okland Californian 60/120° amphibole cleavage Blueschist facies Euhedral glaucophane Glaucophane Glaucophane schist High-Pressure Metamorphism Low-Temperature Metamorphism metamorphic Na-bearing amphibole Pleochroism (blue to lavender) Porphyroblastic texture schist Sodic amphibole Subduction complex Subduction zone metamorphism https://bereket-haileab.geology.sites.carleton.edu/files/original/31a940983936e3d66c18be4aa392d23c.jpg 297bff63d0bdbdcf565e76d5b658944a Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-24 Subject The topic of the resource Hornblende Gabbro Description An account of the resource Major Minerals: hornblende, plagioclase, hypersthene, biotite, enstatite Minor Minerals: iron-titanium oxide Mineralogy Comments: hornblende showing perfect two cleavages, 60/120 degrees cleavage Hornblende gabbro is a mafic rock, compositionally similar to gabbro. Hornblende-bearing gabbros are indicative of hydrous, calc-alkaline magmatism typically associated with convergent-margin (arc) environments. Amphibole-rich gabbros often crystallize from water saturated basaltic magmas derived from above a subduction zone. This thin section features some of the most beautiful hornblende and biotite crystals observed so far. Both minerals are cut in various orientations, displaying hornblende's two cleavages at ~60°/120° and biotite's single perfect cleavage. Some biotite grains are oriented perpendicular to the c-axis, and thus lack visible cleavage. Both hornblende and biotite exhibit strong pleochroism, often occur intergrown, and can be easily mistaken for one another by students new to optical mineralogy. Numerous hypersthene (POX) grains are also present, showing either one or two cleavages depending on the cut. Hypersthene displays weak pleochroism. The plagioclase feldspar and associated mafic minerals are predominantly anhedral, suggesting near-simultaneous crystallization under similar temperature conditions. Iron-titanium oxides are abundant and evenly distributed throughout the thin section. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-24. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=bdebcb48111f4ad5a2ede3ecc4aaa4ba" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=bdebcb48111f4ad5a2ede3ecc4aaa4ba">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/13ED1Kk6eEBqWqB_9V7xWTVwJDIzZDFhs/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1HwgstfqldqX0PQM9jBRZo9BAjkNucAZ4/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1TU-iiY7lWHAW3o4ZwepslC1nQaezkAMg/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/198As53GxWv90GUhlEQI0kHUYVJ8g4LPG/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab amphibole cleavage Amphibole-rich Gabbro Biotite Biotite Cleavage Calc-alkaline Gabbro Cleavage Angles (Hornblende 60/120°) Cleavage in Thin Section Enstatite gabbro Hornblende Hornblende gabbro Hydrous Magmatism Hypersthene igneous Iron-Titanium Oxides mafic Pleochroic Minerals Pleochroism plutonic https://bereket-haileab.geology.sites.carleton.edu/files/original/e0824cb47f6a22250df5141724ec03af.jpg 4121800f0c1f9e038bd978e0eb9645d1 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-25 Subject The topic of the resource Staurolite Quartzite Description An account of the resource Major Mineral: staurolite Minor Minerals: muscovite, chlorite Mineralogy Comments: lots of chlorite Thin sections of BH250-25 from Petaca reveal a quartz-rich matrix with sparse, euhedral staurolite porphyroblasts and scattered opaque oxides. The rock is composed of interlocking grains of quartz and staurolite, which occurs as brown, high-relief prismatic crystals. The staurolite is strongly pleochroic, showing pale yellow to brown shades in plane polarized light. Minor amounts of magnetite appear as opaque black grains dispersed throughout the section. Petrologic Significance The presence of staurolite, an aluminum-rich silicate, in association with quartz has important implications. Staurolite is metamorphic index mineral, forming under intermediate to high grade conditions in pelitic rocks. The original bulk composition was rich in clay minerals. The presence of both staurolite and quartz indicates a silica-saturated, Al-rich bulk composition, typical of metapelitic protoliths subjected to elevated pressures and temperatures during regional metamorphism. There are plenty of chlorite (alteration from biotite) in this thin section indicate that the rock is undergoing retrograde metamorphism. Compare BH250-4, BH250-21, BH250-25 with, BH250-27, 27b, 27c, BH250-160 and BH250-183 Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Petaca, New Mexico, USA Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-25. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=48fad20b4e15433d87cbefe0cb635175" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe> <br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=48fad20b4e15433d87cbefe0cb635175">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1fHVETNA2qHCW0YYfboRo6S2CB5mYWvMv/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/11qTtd3peft5xqXBRfZZqGZk0ffh2u5RB/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1LcjZxSGpZIVrmCf97E5jVnirT9_0XNvu/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1pE9HpivHTwpAZnbjVZVMp91Iaxwxo9Ey/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1UJyfV_6fjY0rpk096dungjMt61WAdptE/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1BrvXUCClW14NtOSm7KlMjp0N-iWmwoDw/preview" allow="autoplay"></iframe><br /><br /><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1SqjTxHoVAQS2vc6Hknn_Qouv962PIA5l/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Chlorite metamorphic Metapelite metasedimentary New Mexico pelitic pelitic rocks Petaca quartzite Retrograde Metamorphism Staurolite Staurolite Quartzite https://bereket-haileab.geology.sites.carleton.edu/files/original/94a5460062482ce93ae34ec957508745.jpg f11164ab999ae97417d4b96dfdbdadd8 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-26 Subject The topic of the resource Garnet Staurolite Schist Description An account of the resource Major Minerals: garnet, staurolite, muscovite, biotite, sillimanite Minor Minerals: tourmaline, chlorite Mineralogy Comments: good muscovite and staurolite; small tourmaline Texture: foliation, optic axis figure on quartz, inclusions in garnet Sample BH250-26 likely derives from a pelitic protolith, a fine-grained mudstone or shale, rich in Al, K, and Fe. This is supported by the presence of aluminosilicate minerals (garnet, staurolite, sillimanite) and abundant muscovite and biotite, typical of K- and Al-rich sediments. Trace tourmaline, either detrital or metamorphic, further supports a metasedimentary origin. Metamorphic Mineral Assemblage: Major: Garnet + Staurolite + Muscovite + Biotite + Sillimanite (Make thin sections for SEM work to confirm whether inclusions within muscovite are sillimanite.) Minor: Tourmaline + Chlorite This assemblage reflects Barrovian-type regional metamorphism within the upper amphibolite facies. Chlorite: Likely formed during retrograde metamorphism from biotite or garnet. Tourmaline: May be detrital or have formed from boron-rich fluids during prograde or retrograde phases. Texture and Structural Features: Foliation: Strong, formed by alignment of muscovite and biotite under ductile deformation during regional compression. Garnet Inclusions: Suggest pre-kinematic garnet growth, with “snowball textures” recording early foliation and mineral assemblages. Significance of Staurolite: Staurolite: An index mineral for intermediate-grade conditions. Its coexistence with sillimanite marks a transition zone and suggests breakdown reactions such as. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-26. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=fac66b7bddb54c5fb9ebab4439aa4798" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=fac66b7bddb54c5fb9ebab4439aa4798">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1T2JZEn0YMfz5_TP5LpxRb7x3dZ7u-EvF/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ko4-iLMgCEKBKxNFBdClT2ygGXfdOMXO/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1vyY-yVM3u5DaqAgtpO8_0qlM2nEQZU7O/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1REOVSIpY1MgtpzDDmatNApNwGqWQuDNu/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1pRabJEHOULLCD2W8EufFbkZqfTLiMMI2/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Iychod2UTKaLmp5XdnQLHBjg9ZPkFP7V/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1S65o_swBUpPnUmQC6ieBJSkf_DTqUVLz/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1AnkuZ1idY73zTsZ80U88rdL0Frnjsu4B/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1iSe1_8V08bmaSgM2tPi14FRVor7dMCba/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab Aluminosilicate Minerals Foliation Garnet-Staurolite Schist metamorphic Metapelite pelitic protolith Pre-Kinematic Garnet Retrograde Chlorite schist Snowball Garnet Texture Tourmaline https://bereket-haileab.geology.sites.carleton.edu/files/original/3fdc14a3a7bd5fd61058176bfbc88e02.jpg d33a7a6fc3a626b8c4518d65bf50d222 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-27 Subject The topic of the resource Baraboo Quartzite Description An account of the resource Major Mineral: quartz <br />Minor Minerals: muscovite, sericite, zircons<br /><br />Texture: non-foliated, sugary appearance, glassy luster, well rounded zirons along a line indicating paleo-layering, grain boundary migration, straight or loate grain boundaries, formation of subrains within larger parent grains.<br /><br />Optics: large quartz crystals perfect for optic axis figures, off centered optic axis figure, flash figures and andulos extinction in quartz. <br /><br />The Baraboo Quartzite is a metamorphosed quartz-rich sandstone prominently exposed in the Baraboo Ranges of southern Wisconsin. Stratigraphic and sedimentological analyses reveal abundant cross-bedding, ripple marks, and tidal bedding—especially in the lower portions—indicating deposition in a fluvial-to-shallow marine environment. <p>Petrology and Mineralogy:<br />Sample BH250-27 is representative of the Baraboo Quartzite, consisting of over 90 vol.% quartz. The quartz grains are well-rounded, typically ranging from 0.25 to 2.0 mm in diameter, and display sutured boundaries formed by metamorphic quartz overgrowths during solid-state recrystallization. Accessory minerals occur in trace to minor amounts and include white micas (muscovite–sericite), detrital zircon, and minor opaque oxides.</p> <p>In several thin sections, alignment of rounded zircon grains is visible, likely marking a preserved sedimentary bedding plane from the original sandstone protolith now transformed into quartzite.</p> <p>Cement and Color:<br />Grain surfaces are coated with thin films of iron oxide (hematite), which act as cement and impart the characteristic brick-red color of the rock. There is essentially no carbonate cement; any cementing material is limited to iron oxide and local silica overgrowths from metamorphism. The extreme purity of the quartz framework contributes to the rock’s high hardness and resistance to weathering.</p> <p>Texture and Structure: <br />Primary sedimentary structures such as lamination and cross-bedding are preserved but overprinted by broad crenulations and weak slaty cleavage from low-grade metamorphism. Overall, the rock retains a dominantly sedimentary texture with only subtle metamorphic overprint.</p> <p>Correlative Units: <br />Regionally correlative units of similar age and composition include the Sioux Quartzite of southwestern Minnesota and eastern South Dakota, and the Washington County Quartzite of Iowa.</p> <p>One common and diagnostic feature of the Baraboo Quartzite in thin sections is the presence of sutured boundaries between quartz grains a key textural indicator of the rock’s metamorphic history and recrystallization processes.</p> <p>Sutured (interlocking or serrated) grain boundaries are highly irregular, embayed contacts between adjacent quartz grains that resemble puzzle pieces. Unlike straight or smooth boundaries, these are characterized by lobes and embayments that penetrate neighboring grains, reflecting internal grain boundary migration.</p> <p>These sutures form through solid-state recrystallization during low- to medium-grade regional metamorphism, involving several processes:</p> <ol> <li>Pressure Solution: Quartz dissolves at points of high stress along grain boundaries, especially where grains are in contact. The dissolved silica is transported by pore fluids and reprecipitated in areas of lower stress.</li> <li>Grain Boundary Migration: Quartz grains adjust their boundaries to reduce total interfacial energy, producing interlocking, sutured textures.</li> <li>Dynamic Recrystallization: Under conditions of differential stress (e.g., during folding), dislocation creep and recovery can drive additional grain boundary modification, enhancing suturing.</li> </ol> <p>These sutured grain boundaries indicate moderate metamorphic conditions sufficient for quartz recrystallization but not intense enough to completely erase original textures or form equigranular, polygonal grains typical of higher-grade metamorphism.<br /><br />Quartzite and Human Use Across Cultures and the Fossil Record:<br /><br />Quartzite, a hard and durable metamorphic rock, has been widely used by human societies for grinding, milling, and tool-making due to its abrasiveness, wear resistance, and geological abundance.</p> <p>Quartzite in Eritrea: Milling Grains:<br />In Eritrea and the Horn of Africa, quartzite was traditionally used to make grinding stones and mullers for processing staple grains such as sorghum, barley, millet, and teff. Grain was ground into flour for foods like injera using hand-held stones on flat quartzite slabs. Its hardness (~Mohs 7), rough texture, and local abundance in Proterozoic terranes made it ideal. Archaeological finds from sites like Adulis and Matara confirm quartzite’s long-standing role in food production.<br /><br />Quartzite Use Among Native American Groups:<br />In the Baraboo region of Wisconsin, Native American groups extensively used Baraboo Quartzite, a dense and durable local material, for stone tools. Sample BH250-27d is an example of such quartzite tool use.<br /><br />Quartzite Tools and Hominin Fossils:<br />Quartzite has been one of the most important raw materials for early hominins in making stone tools, which are often found alongside hominin fossils, helping us understand early human behavior, technology, and evolution.</p> <p>Quartzite as a Toolstone: Quartzite’s hardness, durability, and availability made it a preferred material for producing sharp flakes, scrapers, handaxes, and other stone tools. Early human ancestors associated with the Oldowan (2.6 million years ago) and Acheulean (1.76 million years ago) industries frequently used quartzite at African archaeological sites. Quartzite tools are common at key paleoanthropological locations such as Olduvai Gorge (Tanzania) and the Turkana Basin in Koobi Fora and the Nachukwi area of Kenya. With the oldest stone tool dated today is the Lomekwi tools about 3.3 million years old. Older stone tools have also been found at Melka Kunture, Omo, Hadar, and the Middle Awash in Ethiopia.<br /><br />Association with Hominin Fossils:<br />Quartzite tools are often found in direct association with hominin skeletal remains, providing critical context for behavior, tool use, and subsistence. Their presence alongside fossils of Homo habilis, Homo erectus, and other early humans helps establish timelines and cultural phases. These tools often show wear consistent with butchery, plant processing, and other survival activities.</p> <p>Significance in Human Evolution: <br />Quartzite tools represent technological advances in early hominin cognition and manual dexterity. Their durability allows them to survive well in the archaeological record, often outlasting bones and organic materials. The selection and transport of quartzite by early hominins also reveal insights into landscape use, resource selection, and mobility.</p> <p>Summary:<br />Quartzite has been a vital raw material in early human toolkits and is closely linked to hominin fossil sites throughout Africa. These durable quartzite artifacts provide essential evidence of early technological behavior and remain a cornerstone in interpreting the human evolutionary record.</p> See also BH250-27b, 27c and 27d<br /><br /><iframe width="1800" height="100" src="https://docs.google.com/spreadsheets/d/e/2PACX-1vS4nyqCmZQGn3t6vX4g4nhDPwHMBaKrigt1LaY2pykWbBGXB1wNb6FYArx625I-JTtD7lyg4uz1OS1r/pubhtml?gid=1755540624&amp;single=true&amp;widget=true&amp;headers=false"></iframe> Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant Location: Baraboo, Wisconsin, USA GPS Coordinates: 43.419219, -89.895472 Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-27. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=6e5c9919d285405bbd118051e4e71851" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=a90539e285424f74b508b9e5e57200cf">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1y4WC3QzZ6itAwvtGVVivx2X5buYMiqFf/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/163enoN9RoqQ192C40S_FFmff2l2ptYf1/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1TYSnlwRoSLbVOeg72Kbd1fU8I8o3UJba/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1NZJWSD99W2b3-XQrdZlN0qW8UUZ0g_7B/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1odKdP-nd123n4xs8m63pBuHdxWyxO7qP/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1wTj3hQqAipjJ4hMh4DJjxwGyt8bZLYdB/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hyVYU0M6b-jesyNe0EKoxA9vkaMme3Lu/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1URSMA2qvMd16jQBrYHyY3IVA11Ugp4mc/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hli2t2ncIjz-cy-5sYiBDj-eSB6stpC9/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1cXLCsybIXERnu-1dH0Qz0yIeZU368ZTo/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1GOZPSYF8D326NMYecJdsfIRL2OiELCxP/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1PN-O3cPb-JoAarmZAinmmYDKo0bOwTBT/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Baraboo Quartzite Detrital Zircon Early Hominin Tool stone Early Human Technology Early Stone Tools Grain Boundary Migration Grinding Stone Material Hadar Hematite Cement Iron Oxide Coating Koobi For a Lomekwi Low- to Medium-Grade Metamorphism Melka Kunture metamorphic Metamorphosed Quartz Sandstone metasedimentary Middle Awash Nachukwi Oldowan and Acheulean Industries Olduvai Gorge Omo Paleoanthropological Sites Quartz-rich Sandstone quartzite Quartzite Metamorphic Rock Quartzite Tool Use Sericite Sioux Quartzite Sugary Texture Sutured Grain Boundaries Turkana Basin Washington County Quartzite Zircon (detrital) https://bereket-haileab.geology.sites.carleton.edu/files/original/faecf31580dd61a830dd71ee89d9a83f.jpg a35e525363a41c44089c677afd887c52 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-28 Subject The topic of the resource Epidote Skarn Description An account of the resource Major Minerals: epidote, calcite, chlorite Optics: good grains to obtain optic axis figures BH250-28 is a skarn dominated by epidote, calcite, and chlorite. Epidote occurs as granular to prismatic crystals, often displaying a pistachio-green color in hand sample. Epidote grains in this sample are well-suited for obtaining optic axis figures, making it valuable for optical mineralogy study. Epidote shows high relief, strong pleochroism (yellow-green to green), and high birefringence. Epidote-rich skarns commonly form when hydrothermal fluids from a cooling intrusion react with impure limestones or dolostones, producing calcium–aluminum silicate minerals. This sample likely represents a calcic skarn formed under medium- to low-pressure contact metamorphic conditions. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-28. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=0371d6e1ec2c42e99c05b749448f6a34" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=0371d6e1ec2c42e99c05b749448f6a34">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1pytvKw4RyQ9CJWaqZJi6x2Vlva2-Tolq/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1rFm1BaP4MhtZnb4gQqhNPwNM3QLiQBUT/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1EAEa0mREOmGEMaEoVkxhPlT66YPqRk8D/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/118G39adAZo0CV-YnOgdIxSQoWX7xZMio/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1jVIf7Dh2Q01ok7AOaKGbJCFMUrZ7cLhV/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab Calcite Epidote epidote skarn high birefringence high relief metamorphic metasomatic optic axis figure Pleochroism skarn https://bereket-haileab.geology.sites.carleton.edu/files/original/0060a9b4f64ee5c90b05db61a1884269.jpg 09190468122658a3775bcb2e6d1bbbd8 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-29 Subject The topic of the resource Chlorite Schist Description An account of the resource Major Minerals: chlorite, sulfides Minor Minerals: oxide, magnetite BH250-29 is a chlorite schist, a metamorphic rock characterized by a schistose texture dominated by fine- to medium-grained chlorite, giving the hand sample a greenish hue. Sulfide minerals indicate either metamorphism of a sulfur-bearing protolith or later hydrothermal overprinting. Magnetite occurs as an accessory oxide phase, visible under the microscope with the condenser lens inserted. This rock likely formed from mafic igneous protoliths, such as basalt or gabbro, under Low-grade greenschist facies. Chlorite has low birefringence, producing green to light green colors. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-29. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=884210c7bc2d45c7a1cbd290f185cfeb" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=884210c7bc2d45c7a1cbd290f185cfeb">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Of-2jN5ubt6RqsPF7T27H1SF2RrmqhaN/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1EdhLXErXw9oPytJJn7aIKNIVGTokCmoZ/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1M7kgcnDy_M5vFhc9RxNYSTc70WZyY-La/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1yfNDbIwwSg7nnVpRRKZfLredmErj2TNi/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1lhznvTwEPBxEePQrdhGZhN8jMNTXqWr6/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Chlorite chlorite schist green schist Greenschist facies Low birefringence metamorphic schist https://bereket-haileab.geology.sites.carleton.edu/files/original/05c52314680309a2a85f43931ffc2dd7.jpg e549ef08752c9ed3c50c3fa81cb3ef5b Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-30 Subject The topic of the resource Kyanite Schist Description An account of the resource Major Mineral: kyanite Mineralogy Comments: small-size kyanite crystals Texture: perfect kyanite cleavage BH250-30 and BH250-30b – Kyanite Schist These samples are kyanite-bearing schists, composed predominantly of medium- to coarse-grained kyanite within a foliated matrix of quartz, mica, and other accessory minerals. Kyanite, an aluminosilicate polymorph with the formula Al₂SiO₅, is a key metamorphic index mineral. Its stability field indicates formation under high-pressure, relatively low-temperature conditions, typically within the blueschist to amphibolite facies. The presence of abundant kyanite points to a pelitic protolith—metamorphosed aluminum-rich sedimentary rocks such as shale, mudstone, or siltstone. During regional metamorphism, these fine-grained sediments recrystallized under directed pressure, producing the pronounced schistosity and alignment of micas seen in the samples. Kyanite schists often form in convergent margin settings or continental collision zones, where rocks are subducted or deeply buried. The mineral assemblage in BH250-30 and BH250-30b thus records not only the composition of the original sediment but also the tectonic environment and pressure–temperature trajectory of metamorphism. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-30. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=5ed9adddd52f4ea18724eb80e6e260c5" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=5ed9adddd52f4ea18724eb80e6e260c5">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1agvTp6BhsJsNyxCcBHE6zTIrNW3ye3WZ/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1QIb9JmuZSb06yctc5xdLF0sNFkfK5H7X/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1b-Rw3SFI3__NP1_Nc8CvR1Lp8C5FmWbL/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ai-9noM9MHjKWWnOk91YOvKrtTmfP50L/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Aa_qDVrw4y22Ab1EpnI97PI5Z2hdY6O0/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Oo7taVWzNQzR9bUGwVtpZ9V8iDrltEyF/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/19kge3f-5SeRLDciJuZB3ZYy6lbisR5MV/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1uo9v8d4gtgbtBF0HxCFIlH7FCqA68P_8/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/17G4Cf6-q7uHIiaZYXGbpm02aRIQgy47u/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1l3Hepkvl0gjiASY6VdOu3ETJcpsC0WCO/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1OHC_Grfq6Ffl4g1DGE_5glaUtDlGUqAB/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Aluminosilicate Aluminum-Rich Sediment Amphibolite Facies Blueschist facies Convergent Margin High-Pressure Metamorphism Index Mineral Kyanite Low-Temperature Metamorphism metamorphic pelitic protolith Regional metamorphism schist https://bereket-haileab.geology.sites.carleton.edu/files/original/c82af04d2827c0d768f42fa6c30f58db.jpg cbfb6df9678bcabe520c805815795d2d Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-30b Subject The topic of the resource Kyanite Schist Description An account of the resource BH250-30 and BH250-30b – Kyanite Schist (BH250-30b: Kyanite Schist near San Diego, California) Major Minerals: kyanite, staurolite, biotite, chlorite, muscovite, plagioclase, orthoclase, tourmaline, quartz Minor Mineral: zircon Mineralogy Comments: The rock contains massive, bladed kyanite crystals—many reaching several millimeters in length—set within a fine- to medium-grained foliated matrix of mica, feldspar, and quartz. Staurolite is commonly intergrown with kyanite and mica, while tourmaline occurs as prismatic, pleochroic grains. The thin section of BH250-30b contains the highest concentration of zircon observed among the BH250 samples. Many zircons display distinct pleochroic halos on chlorites and biotite, caused by radiation damage to surrounding minerals during zircon decay—a useful petrographic indicator of radioactive mineral inclusions. Biotite is well-developed, with several grains cut perpendicular to the c-axis, allowing for clear observation of interference figures under conoscopic examination. Muscovite and chlorite are commonly aligned along the foliation, contributing to the rock’s schistose texture. The mineral assemblage reflects a high-pressure, low- to moderate-temperature metamorphic environment, consistent with the stability field of kyanite and staurolite, and indicative of a pelitic protolith. Coverage The spatial or temporal topic of the resource, the spatial applicability of the resource, or the jurisdiction under which the resource is relevant San Diego, California, USA Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 30b. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=bc787664f38e4b8ebd505de05b951ed9" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=bc787664f38e4b8ebd505de05b951ed9">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ZA5_4ECedGZhShli1yVnwLfvwSiijPFh/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1ACoXLVshAIPKSUwPbqCDfuVB7dqitE8V/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1cTwNQ_eAT1IjR9qVDTN-CBpoUFSGcTqx/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1vgqQfnBn1Mwiq9Oh0tqNzF8HTI7kAFXV/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1vzQf2RroLcT9uhL86nSqjZJl8VmXePns/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1XYNERrd8s8KaFlQWj-uLd1LOusvwbf0o/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/19t_Tjx8PFJDIeydNUZ1BHgYcmYd7cI0p/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/1Giq8FAwCr_k8ZIUT38fkX7F5DlEGS8XU/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/1UC6e2esnts1Vde38cffEeUiRnnthWFdH/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/1_LyoWCFv5Bdqgi_F8NbJZExAqEaI3z3S/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/1tX1ZNw28edtxUnJqKaPay7mduFzYYV-_/preview" allow="autoplay"></iframe> <iframe width="100%" height="480" src="https://drive.google.com/file/d/1smObTYCBvxXow9W6C9BfxGcBRIFVkggy/preview" allow="autoplay"></iframe> src="https://drive.google.com/file/d/1XD-Kz0eBydtyXn1BPPOfEn9p3hlpcXNk/preview" allow="autoplay"&gt;<br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1uEWeXNnE3Q7D9II1VzlVf4CFZBhjXwJv/preview" allow="autoplay"></iframe> &lt;iframe width="100%" height="480" Creator An entity primarily responsible for making the resource Bereket Haileab Aluminosilicate Aluminum-Rich Sediment Amphibolite Facies Biotite Blueschist facies Chlorite Convergent Margin Foliation High-Pressure Metamorphism Index Mineral Interference figures Kyanite Low-Temperature Metamorphism metamorphic muscovite pelitic protolith Pleochroic halo Regional metamorphism San Diego Geology schist Staurolite Tourmaline Zircon https://bereket-haileab.geology.sites.carleton.edu/files/original/96cb1cb51e97dd450a5f98a6ae18c740.jpg e1ae7bdffa457720bdb57b4caee9bf8f Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-31 Subject The topic of the resource Talc Tremolite Schist Description An account of the resource BH250-31 is a metamorphic rock dominated by talc and tremolite. Numerous talc grains are cut perpendicular to the c-axis, allowing excellent interference figures to be observed. Talc displays a BXa(x) biaxial negative interference figure on sections cut perpendicular to the optic axis and shows high birefringence on grains in other orientations. Talc’s birefringence is similar to that of muscovite, but it is distinguished by its characteristically small 2V angle. Tremolite, also biaxial negative, typically forms during the metamorphism of calcium and magnesium rich sedimentary rocks such as dolostone and limestone, whereas muscovite generally develops from aluminum-rich protoliths. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-31. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=ee24cc7812344639b6dd4a1a8496dd56" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=ee24cc7812344639b6dd4a1a8496dd56">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/149MLVkkr0ly8IJx7apMROF9O7Hq3tdPI/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1tuiiR--GdIEkAqz0hwWQTA7Xd98QI5EO/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/159YkKYV1dlHrh0jmLhOYf7ZNhnNAxs3g/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/16tixiecHCqGsAOJBGpxSPukF64NgQOCJ/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1I3oXtuEtPW3eOGtyXVciQ1OH3Ba8i14G/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Acute Bisectrix Biaxial negative BXa high birefringence interference figure metamorphic schist Small 2V angle Talc Tremolite https://bereket-haileab.geology.sites.carleton.edu/files/original/444be69b544bb8a196c09cdb82f17051.jpg d2c5b644e4a20523e8bd90448a8338ba Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-32 Subject The topic of the resource Serpentinite Description An account of the resource Major Mineral: serpentine Minor Mineral: oxide BH250-32 is serpentinite, a metamorphic rock composed almost entirely of minerals in the serpentine group. It forms when ultramafic rocks, such as peridotite or dunite, are altered by hydrothermal fluids or seawater. Under the microscope, serpentinite exhibits low birefringence and typically shows a fibrous or platy habit. Mesh textures, formed by the pseudomorphing of olivine, are common. Metamorphic Grade: Low-grade metamorphism, often within the greenschist facies. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample 32. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=6a6442ce1a1248348e86a42e4fc5d166" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=6a6442ce1a1248348e86a42e4fc5d166">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/10z8gARniUAyVz1vCgajtFrX8S0x7yNc6/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1L1PSKe0UU4wl6lzG9SRK-UyngkgAv5tk/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1WOW1na-uRl6FvBdGAeqUXWQ-xFtKhiMZ/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1s6ZbBiFqKQYWsvHXVVPW0wLBq8m1jBxf/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Fibrous Habit Hydrothermal alteration Low birefringence Low-grade metamorphism metamorphic serpentinite ultramafic alteration https://bereket-haileab.geology.sites.carleton.edu/files/original/df9ac4f2a41ef384b320088c4a6c7cce.jpg 25a83a661abd93f49cf0101b32815b08 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Igneous Rocks Subject The topic of the resource This collection covers both volcanic and intrusive rocks, including rhyolites, granites, diorites, andesites, basalts, gabbros, diabases, pumices, obsidians, syenites, phonolites, peridotites, carbonatites, dacites, trachyte, dunites, xenoliths, ignimbrites, and pegmatites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section and hand sample Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-33 Subject The topic of the resource Sodalite Description An account of the resource Major Mineral: Sodalite Minor Minerals: Oxides BH250-33 is a rock full of Sodalite minerals. Optical Character: Sodalite is isotropic, belonging to the cubic crystal system. Under plane-polarized light (PPL), it typically appears blue with low relief and generally shows no birefringence. It may exhibit a faint bluish tint in PPL, but remains isotropic under cross-polarized light. General Information: Sodalite is a relatively rare, blue-colored tectosilicate mineral within the feldspathoid group. It commonly forms in silica-undersaturated, alkaline igneous rocks such as nephelinite, phonolite, and sodalite syenite. Sodalite typically occurs in environments where quartz is absent or very scarce and is often associated with other feldspathoids like nepheline, leucite, cancrinite, and also with feldspar. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-33. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section and hand sample Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=d6eca2a9e14b4c8a90b1eb9871b4d045" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=d6eca2a9e14b4c8a90b1eb9871b4d045">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hZbzDSmWeIb1a_H6IC64gr6oO1mb8Bkp/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1y5bcKqtTXuVP0mURwltZiwRaucSjCG3M/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1P0T6P95gEeeEmvGw8Hmmd1AN7Q_e3_z8/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1YkVyhsjPcALqLWqZoWK1bVnVmhFrcDPC/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Alkaline igneous rock Blue under PPL Feldspathoid igneous Isotropic mineral Low relief mafic phonolite plutonic Silica-undersaturated rock Sodalite Sodalite syenite https://bereket-haileab.geology.sites.carleton.edu/files/original/17962425e782e33095a6ed6d22600e4c.jpg 6f30f0d3336ac2bd5881640fa31be795 Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Metamorphic Rocks Subject The topic of the resource This collection includes slates, phyllites, schists, gneisses, eclogites, marbles, quartzites, skarns, granulites, and mylonites. Creator An entity primarily responsible for making the resource Bereket Haileab Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs, chemical analyses (major elements, trace elements and REE analyses for selected samples). Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-34 Subject The topic of the resource Garnet rich immature "sandstone" Description An account of the resource Major Minerals: garnet, orthopyroxene Minor Minerals: plagioclase, chlorite Sandstone is one of the most common sedimentary rocks and plays a critical role in sedimentary geology, stratigraphy, petroleum geology, and hydrogeology. It is a clastic sedimentary rock composed primarily of sand-sized particles (0.0625 to 2 mm in diameter), cemented together by a matrix of finer particles and/or chemical cement. The most abundant mineral in sandstone is quartz, valued for its hardness and chemical stability. Feldspars—both plagioclase and K-feldspar—are also common, particularly in arkosic sandstones, although they are less chemically stable than quartz. Sandstones often contain lithic fragments, which are pieces of pre-existing igneous, metamorphic, or sedimentary rocks. Accessory minerals may include micas (muscovite and biotite), zircon, tourmaline, magnetite, and garnet. The mineralogical composition of sandstone provides essential clues about its provenance. Provenance analysis is a powerful tool in reconstructing sediment transport pathways and inferring tectonic settings. Cementation and Diagenesis: Cementation is a diagenetic process whereby minerals precipitate in the pore spaces between grains, binding them together. Common types of cement include: Silica (cryptocrystalline silica/quartz overgrowths) Calcite (CaCO₃) Iron oxides (e.g., hematite, goethite) Clay minerals, such as Fe-rich illite (glauconite) Sandstone Classification Sandstones are classified based on grain composition and matrix content: By Grain Composition (QFL: Quartz–Feldspar–Lithic Fragments): Quartz arenite: >90% quartz Arkose (feldspathic arenite): >25% feldspar Litharenite: >25% lithic fragments By Matrix Content: Arenite: Clean sandstone with <15% matrix Wacke: Mud-rich sandstone with >15% matrix (e.g., graywacke) Depositional Environments Sandstones form in a range of depositional environments, including: Fluvial Aeolian Shoreline/Beach Deltaic Deep-marine (e.g., turbidites) BH250 Sandstone Collection The BH250 collection includes thirteen sandstone samples collected from southeastern Minnesota and from geology field trips across the Midwest, South Dakota, the Grand Canyon, and Death Valley. Each sample is accompanied by hand specimens, thin sections, and photomicrographs, providing an excellent foundation for detailed petrographic analysis. Here you will find short descriptions for each sandstone sample. BH250-34 was collected by Bill Dinklage and it has angular fragments of garnet that make up this very immature sedimentary rock which is hard to call is sandstone. BH250-34 is an exceptionally immature sandstone sample collected by Bill Dinklage. It is dominated by angular garnet grains, along with orthopyroxene, plagioclase, and chlorite, indicating a proximal source area and minimal sedimentary transport. The coarse grain size and angularity of the garnet fragments suggest that this rock borders on a garnet-rich sediment or metamorphic rock that is weathering and delivering these sediments. This sample represents a highly mineralogically immature clastic rock, lacking the quartz dominance typical of most sandstones. Its composition points to derivation from a high-grade metamorphic or mafic igneous source. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-34. Housed at Carleton College in Minnesota. Contributor An entity responsible for making contributions to the resource Bereket Haileab Bill Dinklage Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=ded90be3a8fb4be280f70ac7eec28ef6" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=ded90be3a8fb4be280f70ac7eec28ef6">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/14tNcwJo7kitX828Ctp9MsLZBIc2Q59hY/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1Syognm6MpBX1Vj3GViHpc1hrji7Ua65S/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1zEw4SeQLxslK2j5yQuNN3VhFmHtrDZ7h/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1GeIAP-AimDapGaK166wynwhyt4lMLI0Q/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Angular grains Clastic sedimentary rock Garnet Garnet-rich sandstone granulite High-energy depositional environment Immature sandstone Immature sediment Limited diagenesis Low transport distance Mafic-derived sediment metamorphic Metamorphic provenance Orthopyroxene Provenance & Source Rock Proximal deposition https://bereket-haileab.geology.sites.carleton.edu/files/original/75e5e4d6ebd52393edba2d621383a961.jpg c7c1b937941f4f21a0d0edee0ba7e56d Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Mineral Optics Gallery Subject The topic of the resource This collection contains minerals cut perpendicular to the c-axis in thin section. Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs. Contributor An entity responsible for making contributions to the resource Bereket Haileab Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-35 Subject The topic of the resource C-axis Quartz Description An account of the resource Major Mineral: Quartz Mineralogy Comments: Quartz grain cut perpendicular to the c-axis. Optics: A centered optic axis figure shows a black cross (isogyres) with its center—the melatope—marking the emergence of the optic axis. No isochromes are present. Interference colors display addition (blue) in quadrants I and III, and subtraction (yellow) in quadrants II and IV, confirming a uniaxial positive optic sign. The BH250 collection includes a diverse range of rocks, from quartzites to granitic types, many of which contain quartz. In these samples, quartz grains cut perpendicular to the c-axis are common, allowing for the observation of clear interference figures. Off-centered optic axis figures and flash figures can also be frequently obtained in thin section. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-35. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=54638367e11c46e9981f28d2fe93b190" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=54638367e11c46e9981f28d2fe93b190">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1IrloBnuzw9pwEqEgdqcoe0CKKts_amgk/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1hknhTpvtVyF93Sg7SHPzQgwRe2sU5LEc/preview" allow="autoplay"></iframe><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1M01uUFJn76QVDxOOOY47s-fuUPtV0V2M/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Addition and subtraction Interference Colors Mica plate optic axis figure optical Optically positive Polarized Light Microscopy Quartz Uniaxial Positive Yellow colors in 2nd and 3rd quadrantes https://bereket-haileab.geology.sites.carleton.edu/files/original/3ed889d55b981b84d1d753ba60cfa540.jpg 0cf97f0e0e6825c1cf8d2d9d792da12f Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Mineral Optics Gallery Subject The topic of the resource This collection contains minerals cut perpendicular to the c-axis in thin section. Source A related resource from which the described resource is derived Housed in Anderson Hall, Carleton College. Format The file format, physical medium, or dimensions of the resource Thin sections, thin section scans, hand samples, hand sample images, photomicrographs. Contributor An entity responsible for making contributions to the resource Bereket Haileab Thin section Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource BH250-36 Subject The topic of the resource C-axis Calcite Description An account of the resource Major Mineral: Calcite Mineralogy Comments: Calcite grain cut perpendicular to the c-axis. Optics: A centered optic axis figure displays a black cross (isogyres) with a central point—the melatope—indicating the emergence of the optic axis. Surrounding the melatope are concentric rings of interference colors known as isochromes. Due to calcite’s high birefringence (~0.172), multiple isochromes are visible and well defined. Calcite is optically uniaxial negative. When viewed with a sensitive tint plate (mica), addition (yellow) appears in quadrants II and IV, and subtraction (blue) in quadrants I and III, consistent with a uniaxial negative mineral. However, using a quartz wedge reverses these interference color changes: subtraction occurs in quadrants II and IV, and addition in quadrants I and III. The BH250 collection includes a variety of rocks such as marbles, skarns, and amygdaloidal basalts with secondary minerals filling cavities, many containing calcite. In these samples, calcite grains are often oriented perpendicular to the c-axis, facilitating clear observation of interference figures. Because of calcite’s high birefringence, sections cut perpendicular to the c-axis do not appear isotropic and never go completely dark under crossed polars. Off-centered optic axis figures are also commonly observed, where the melatope is displaced from the center and portions of the isogyre sweep in and out of the field of view during stage rotation. Comparison: Compare the optics observed in BH250-36 with those in BH250-103b (marble). In BH250-36, the orientation is ideal and the interference figure is perfectly centered and easy to interpret. In contrast, BH250-103b requires careful grain selection; many grains will show slightly off-centered optic axis figures, partial isogyres, or only near-optic-axis conditions. This comparison highlights the difference between a textbook example and the more realistic challenge of identifying and interpreting interference figures in natural rocks. Source A related resource from which the described resource is derived From the rock collection of Bereket Haileab. Sample BH250-36. Housed at Carleton College in Minnesota. Type The nature or genre of the resource Thin section Relation A related resource <iframe width="100%" height="600" style="border: 0;" src="https://carleton.maps.arcgis.com/apps/instant/media/index.html?appid=3830c9fdbb0d4d438435a5df3bb2e8fd" frameborder="0" allowfullscreen="allowfullscreen">iFrames are not supported on this page.</iframe><br />View on ArcGIS Online <a href="https://carleton.maps.arcgis.com/home/item.html?id=3830c9fdbb0d4d438435a5df3bb2e8fd">here</a><br /><br /><iframe width="100%" height="480" src="https://drive.google.com/file/d/1PC5_J8P9_HSQuTdMjLUuDq49g0Z6UqB5/preview" allow="autoplay"></iframe> <iframe width="640" height="480" src="https://drive.google.com/file/d/1ifLtt5cGVYig4uVQKDPJoegy0CLN9mUW/preview" allow="autoplay"></iframe> <iframe width="640" height="480" src="https://drive.google.com/file/d/1Qym82xrlKsMc2Om_vZO7z3Vw8Q1RMuPe/preview" allow="autoplay"></iframe> Creator An entity primarily responsible for making the resource Bereket Haileab Contributor An entity responsible for making contributions to the resource Bereket Haileab addition quadrants Bertrand lens birefringence birefringence 0.172 C-axis calcite Calcite carbonate centered optic axis figure conoscopic observation crossed polars fast ray high birefringence Interference Colors Isochromes Isogyres Melatope Mica plate off-centered optic axis figure Optic Axis optic axis figure optical Optically negative plane polarized light PPL Quartz Wedge Sensitive Tint Plate slow ray subtraction quadrants uniaxial mineral Uniaxial negative vibration directions XPL Yellow colors in 1st and 3rd quadrants Addition and subtraction