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