Browse Items
- (titanite)
- #Granite
- 100% Mg-end member olivine
- 2.4 refractive index
- 2nd order interference colors
- 2V ~90°
- 2V angle
- 2V Angle Identification
- 2V measurements
- 2V(x) of 18 degrees
- 4.4 billion years
- 56° and 124° cleavage
- 60/120° amphibole cleavage
- Abitibi Greenstone Belt
- Absaroka volcanic field
- Accessory minerals
- accessory minerals:
- Accessory phosphate minerals
- Accretionary lapilli
- Acheulean industry
- acicular habit (contextual)
- Acicular olivine
- Acute Bisectrix
- Acute Bisectrix Figure
- adamellite
- adcumulate
- Adcumulates
- Addition
- Addition and subtraction
- addition colors
- addition of retardation
- addition quadrants
- Aegirine
- Aegirine anomalous interference colors
- Aegirine Augite
- Aegirine pleochroism
- Aegirine-augite
- Aegirine-augite birefringence
- Agglomerated crystals
- agglutinate
- Aksum Obelisks
- Aksumite Civilization
- Al₂O₃-rich shale
- Alaska
- Alaska Geology
- albite
- albite twining
- Albite twinning
- Alfred Wegener
- aligned feldspar laths
- Alkali basalt
- alkali feldspar
- Alkali feldspar replacing leucite
- alkali-rich magma
- Alkali-Rich Volcanic Rock
- alkaline basalt
- Alkaline clinopyroxene
- Alkaline complex
- Alkaline igneous rock
- alkaline igneous rocks
- Alkaline igneous suite
- alkaline intrusion
- Alkaline magmatism
- Alkaline plutonic rock
- Alkaline pyroxene
- Alkaline pyroxene birefringence
- Alkaline Series
- alkaline volcanic rock
- alkaline volcanism
- allanite
- allanite alteration
- Alta stock
- Alta stock marble
- Alta Utah
- Alteration (sericite
- alteration textures
- altered igneous rock
- Altered Mafic Minerals
- Altered olivine
- altered surface
- Altmühltal Formation
- Alumino silicate Minerals
- Aluminosilicate
- Aluminosilicate Minerals
- Aluminous protolith
- Aluminum-rich metamorphic minerals
- aluminum-rich metamorphic rock
- Aluminum-Rich Sediment
- Amnicon Falls State Park
- amphibole
- Amphibole Alteration
- amphibole breakdown
- amphibole cleavage
- Amphibole cut perpendicular to the b-axis
- Amphibole cut perpendicular to the c-axis. Amphibole cut perpendicular to the a-axis
- Amphibole group
- Amphibole pleochroism
- amphibole reaction rim
- amphibole schist
- Amphibole-rich Gabbro
- Amphiboles
- amphibolite
- Amphibolite Facies
- Amphibolite to Granulite Facies
- Amphibolitized Intrusion
- Amygdaloid formation
- Amygdaloidal basalt
- Amygdaloidal texture
- Amygdule
- Amygdules
- Analcime
- Ancient mantle melting
- Ancud Volcanic Complex
- Andalusite
- Andalusite extinction
- andesite
- angular fragments
- Angular grains
- Anhedral Plagioclase
- Anhedral plagioclase feldspars
- Anhedral pyroxene
- anhedral pyroxenes
- Ankaramite
- Anomalous interference colors
- anomalous optical behavior
- Anorthite
- anorthosite
- Anoxic depositional environment
- Antarctic geology
- Antarctica
- Antartica
- Antiperthite
- Apatite
- Apatite in Amphibole
- Apatite radiation damage
- Aphanitic Texture
- Aquifer
- Arabian-Nubian Shield
- Aragonite
- arc magmatism
- Archaeological tool use
- Archean craton
- Archean Gneiss
- Archean Granite
- Archean greenstone belt
- Archean komatiite
- Archean volcanic rock
- Archean volcanism
- Archean-Proterozoic Basement
- Arkosic Sandstone
- ash
- ash deposit
- ash matrix
- ash-flow deposit
- ash-flow deposition
- Ash-flow tuff
- Augite
- Augite core with aegirine rim
- Australia
- Australia komatiite sample
- Authigenic minerals
- Baked contacts
- Balsam
- Balsam NC
- Bancroft Ontario
- Banded Gneiss
- Banded Iron Formation
- Banded Iron Formation (BIF)
- banded iron formation clasts
- Baraboo
- Baraboo basin evolution
- Baraboo Quartzite
- Baraboo Quartzite context
- Baraboo Range
- Barite
- Barrovian metamorphism
- basal Baraboo Quartzite
- Basal Cambrian unit
- basalt
- basalt clasts
- Basalt flows
- Basalt glass
- basalt protolith
- Basalt with secondary mineralization
- Basaltic
- Basaltic Andesite
- basaltic composition
- Basaltic dike
- basaltic eruption
- basaltic glass
- Basaltic hornblende
- basaltic intrusion
- Basaltic lava flow
- basaltic scoria
- basaltic trachyandesite
- Basaltic volcanic glass
- basaltic volcanism
- basanite
- basanites
- Base metal deposits
- Basin and Range Province
- Bass Limestone
- Bavaria
- Baxter Hollow
- Baxter Hollow Granite
- Bearpaw Green Porphyry
- Bearpaw Mountains
- Bearpaw Mountains geology
- Beartooth Mountains
- Beck Spring Dolomite
- Becke line method
- Belbel
- Belview MN
- Benmoreite
- Bentonite
- Berlin Blue
- Berlin Blue Interference color
- Berlin blue interference colors
- Bertrand lens
- BH250-227d
- BH250-231b
- BH250-231c
- biaxial
- Biaxial Mineral
- Biaxial negative
- biaxial neutral
- Biaxial Optics
- BiaxialPositive
- BIF
- BIF fragments
- Big Island geology
- Big Island Hawaii
- Biochemical sedimentary
- Biogenic limestone
- Biogenic mineral formation
- Biogenic origin
- Biotite
- Biotite (Fe-Mg varieties)
- Biotite alteration
- Biotite Cleavage
- Biotite optic axis figure
- Biotite pleochroism
- Biotite Stability
- Biotite to chlorite alteration
- Biotite-muscovite schist
- Biotitization
- bioturbation
- Bird's eye
- Bird's-Eye Extinction
- Bird’s eye maple extinction
- Bird’s eye maple interference colors
- bird’s-eye biotite
- Bird’s-eye maple extinction (biotite)
- birefringence
- birefringence 0.172
- birefringent mineral
- Bivalves
- Biwabik Iron Formation
- Black Hills
- Black Hills geology
- Black Hills metamorphic core
- Black Hills South Dakota
- Black limestone
- Black Vishnu Schist
- Bladed Crystals
- Bladed kyanite
- Bladed texture
- blue addition
- Blue Calcite
- blue quadrants
- Blue Schist
- Blue under PPL
- Blueschist facies
- blueschist-related rock
- Bolsena
- Bolsena Civita Castellana
- bomb sag
- Botolan
- Botryoidal texture
- Bottleneck texture
- Boudinage
- Bowen’s Reaction Series
- Brachiopods
- breccia
- Brecciation
- Brighton
- Brighton Formation
- brittle deformation
- Brittle mica
- Bronzite
- Brucite
- Bryozoans
- bubble wall junction
- Buffalo Luxury Camp
- burrows
- BXa
- BXa optic axis
- BXA Optic Figure. BXO Optic Figure
- BXa(x)
- C-axis calcite
- C-axis cut
- C-axis orientation
- Calc-alkaline Gabbro
- Calc-Alkaline Magma
- calc-silicate
- calc-silicate alteration
- Calc-Silicate Minerals
- calcic plagioclase
- calcic-amphibole
- Calcite
- Calcite (vesicle fill)
- calcite group
- Calcite Polymorph
- Calcite Recrystallization
- Calcite veins
- Calcite vs Aragonite
- Calcite-cemented sandstone
- Calcite-filled voids
- Caldera-forming eruption
- California geology
- Cambrian
- Cambrian Sandstone
- Cambrian shoreline
- Canada
- Canadian geology
- Canadian Shield
- Canary Islands
- Cannon River Wilderness Park
- CaO geochemistry
- cap carbonate
- Carbonaceous material
- carbonate
- carbonate concretions
- Carbonate deposits
- Carbonate Metamorphism
- carbonate mineral
- Carbonate Minerals
- Carbonate petrography
- carbonate platform
- Carbonate Protolith
- Carbonate Protolith Metamorphic Mineral Assemblage
- Carbonate Replacement
- Carbonate rock
- carbonate to clastic transition
- carbonate weathering comparison
- carbonate-rich
- carbonatite
- Carleton College Arboretum
- Carlsbad twinning
- Carlton Mn
- Caron Park
- Carrara Formation
- Cascade Range
- Cataclasite
- cataclastic breccia
- Cavity Fill Minerals
- Cedar Valley Group
- cementation
- Cenozoic
- centered optic axis figure
- Cephalopods
- chadacryst
- Chalcedonic silica
- Chalk
- Chalk Group
- Chemical precipitation (Fe–Mn crusts)
- chemical weathering
- Chert
- chert nodules
- Chiastolite
- Chile
- Chilled margin
- Chilled margins
- Chlorite
- Chlorite (pennite)
- Chlorite (pennite) with berlin blue interference colors
- Chlorite alteration
- Chlorite Optics
- chlorite schist
- Chlorite-rich vesicle fill
- chlorite)
- chloritization
- Chloritoid
- Chloritoid schist
- Chloritoid-Garnet-Mica Schist
- chromatic bands
- chromium
- Cima volcanic field
- cinder cone
- Civita Castellana
- clast-supported
- Clastic sedimentary rock
- Clay alteration
- Clay Mineral
- Clay Mineral Formation
- Clay-derived Cement
- Clean carbonate protolith
- Cleavage 60/120
- Cleavage Angles (Hornblende 60/120°)
- Cleavage in Thin Section
- Climate change archive
- Clinopyroxene
- Clinopyroxene (CPX)
- Clinopyroxene inclusions
- Clinopyroxenite
- CO2-rich magma
- Coarse-grained
- Coarse-grained igneous rock
- coarse-grained intrusive rock
- Coccolith limestone
- Coccolith-rich
- coesite
- coesite eclogite
- Colorado
- Colorado River Geology
- columnar joint
- complete alteration
- Compositional maturity
- Compositionally mature
- Concentric ash structures
- Concentric banding
- Concentric carbonate layers
- Concentric mineral zoning
- concentric rings
- Concentric zoning
- Concentric zoning in amygdule
- conchoiial fracture
- conductive cooling
- cone climbing
- Confusion Point
- conglomerate
- Conjugate fractures
- conoscopic illumination
- conoscopic image
- conoscopic interference pattern
- conoscopic observation
- Conoscopic Optics
- Contact Metamorphic Deposit
- contact metamorphism
- Continental Collision
- Continental crust magmatism
- continental drift
- Continental hotspot
- Continental rift setting
- continental rifting
- Convergent Margin
- Cooke City Montana
- cooling rate
- Copper mineralization
- coral fossil
- cordierite
- Corona Texture
- Corona textures
- coronitic texture
- corundum
- corundum deposits
- country rock fragments
- Crenulation cleavage
- Crestmore Blue Calcite
- Crestmore Quarry
- Cretaceous
- Crinoids
- cristobalite
- Cross-cutting Relationships
- cross-hatched twinning
- crossed polars
- Crustal Evolution
- crustal thickening
- crustal xenoliths
- Cryogenian
- Cryogenian climate
- Cryptocrystalline
- Cryptocrystalline quartz
- Crystal Differentiation
- crystal glass interaction
- Crystal Growth
- Crystal Growth Sequence
- crystal mush
- crystal nucleation
- Crystal Replacement
- Crystal Settling
- crystal tuff
- Crystal zoning
- crystallization
- crystallographic phase transition
- cubic leucite
- cubic symmetry
- Cubic to tetragonal leucite
- cubic to tetragonal transition
- Cummingtonite
- Cummingtonite Schist
- cummingtonite-grunerite series
- cumulate
- cumulate layering
- cumulate rock
- Cumulate texture
- cumulate textures
- Cuneiform Texture
- dacite
- dark cross (Maltese cross)
- Dark Shale
- Deadwood formation
- Death Valley
- Death Valley geology
- Death Valley mining history
- Death Valley National Park
- Death Valley region
- Death Valley stratigraphy
- Debitage
- debris flow
- Decarbonation Reaction
- Decorah Shale
- deep burial
- Deep Chemical Weathering
- Deep crustal alkaline complex
- deep crustal metamorphism
- Deep-sea basalt
- Deformation microstructure
- deformation twins
- deformed granite
- Deformed Quartz
- Dehydration reaction in amphiboles
- Dehydration Rim
- Depleted mantle
- desert geology
- Detrital Minerals
- Detrital Zircon
- devitrification
- devitrification textures
- Devitrified Glass
- diabase
- diabasic texture
- Diagenesis
- diagenetic recystallization
- Diagnostic nepheline optics
- diamictite
- diatreme
- Diatreme Rock
- Differentiated igneous complex
- differentiated magma
- Digital Microscope Scan
- dike
- dike crystallization
- dike emplacement
- Dike offset
- Dike–fault interaction
- Diopside
- Diopside twining
- diorite
- Discovery Harbor
- Disequilibrium Crystallization
- disequilibrium texture
- Dish Hill
- Dish Hill xenolith
- displaced volcano
- Displacement
- Distal tephra
- Divergent plate boundary
- dolerite
- Dolomite
- Dolomite Breakdown
- Dolomite plus quartz reaction
- Dolomitization
- dolostone
- Dolostone Hidden Falls Member Platteville Limestone Dolomite Dolomitization EDS Mapping Conchoidal fracture Warsaw Township
- Dolostone protolith
- dropstone
- dropstones
- Ductile deformation
- Duluth
- Duluth Complex
- Duluth Gabbro
- Duluth Gabbro Complex
- dunite
- Early diagenesis
- Early Earth mantle
- Early Earth volcanism
- Early Hominin Tool stone
- early human evolution
- Early Human Technology
- Early Ordovician
- Early stone age
- Early Stone Tools
- East African archaeology
- East African Humid Period
- East African Orogeny
- East African Rift
- East African Rift System
- East African Rift tephra
- East Pacific Rise
- eclogite
- eclogite facies
- Egan Chute
- Egypt
- Eldes Corner
- Element Mobility
- Elk Creek Trail
- elongate crystals
- elongated amphibole in thin section
- Emigrant Pass
- Emplacement dynamics
- Emplacement History
- Enclaves
- English Channel coast
- Enstatite
- Eocene
- Eocene volcanism
- Epidote
- epidote skarn
- equigranular
- Equilibrium crystallization
- Eritrea
- Eritrea quartzite use
- ETH-86-333
- Ethiopia
- Ethiopian
- Ethiopian Highlands
- euhedral
- Euhedral crystals
- Euhedral garnet
- Euhedral glaucophane
- euhedral leucite
- Euhedral nepheline
- euhedral olivine
- euhedral perovskite
- euhedral phenocrysts
- euhedral plagioclase
- Euhedral pyroxene
- euhedral pyroxenes
- euhedral siderite
- Euhedral spinel crystals
- Euhedral Zircon
- europium anomaly
- eutaxitic fabric
- Eutectic crystallization
- eutectic relationships
- evolved magma
- exhumation
- exhumation textures
- Explosive volcanic eruption
- explosive volcanism
- Exsolution
- Exsolution lamellae
- Exsolution texture
- Extinction zoning
- Faint pleochroism (hypersthene)
- Fan-Shaped Crystal Growth
- Fan-shaped zeolite
- fast axis
- fast ray
- fast ray direction
- fault breccia
- fault offset
- fault zone rocks
- Faulted dike
- Fe-Mg amphibole
- Fe-Mg rich metamorphic rock
- Fe-Mg rich rocks
- Fe-rich Carbonatite
- Fe-Ti oxides
- Fe–Mn crust formation
- Fe–Mn oxide precipitation
- FeCO₃
- Feldspar
- Feldspar alteration
- feldspar deformation
- Feldspar exsolution
- Feldspar intergrowth
- Feldspar Phenocrysts
- Feldspar weathering
- Feldspar-rich sandstone
- Feldspathoid
- feldspathoid instability
- Feldspathoid minerals
- feldspathoid stability
- Feldspathoid volcanic rocks
- Feldspathoid-bearing rock
- Feldspathoid-rich rock
- felsic
- Felsic Gneiss
- felsic igneous rock
- felsic intrusive rock
- felsic magma
- Felsic Volcanic Rock
- felsic volcanism
- felsic xenoliths
- ferric iron
- ferrihydrite
- ferromagnesian minerals
- Ferromagnesian silicates
- ferrous iron
- fiamme
- Fibrolite
- fibrolitic sillimanite
- fibrous crystals
- fibrous glass
- Fibrous Habit
- Fibrous texture
- Field Relationships
- filamentous
- filamentous glass
- fine grained groundmass
- fine volcanic glass
- Fine-grained basalt
- Fine-grained carbonate
- fine-grained groundmass
- fine-grained limestone
- fine-grained sedimentary rock
- fine-grained sedimentary rocks
- Fine-grained silica
- first-order colors
- fish fossil
- Fish-tail garnet
- Fissile sedimentary rock
- Fissile shale
- fissility
- Fissure 8
- fissure eruption
- Flagstaff Arizona
- Flagstaff Geology
- Flame Perthite
- Flash figures
- flat
- flattened pumice
- flint
- flow alignment
- flow banding
- flow texture
- Flow-Aligned Feldspar
- fluid alteration indicator
- fluid flow
- fluid pathways
- Fluid-rock interaction
- Fluorellestadite
- Fluorescent Minerals
- fluorite
- Fluorite (with purple zoning)
- Fo-rich olivine
- foamy texture
- Foid-bearing intrusive rock
- Foliated Metamorphic Rock
- foliated quartzite
- foliated rock
- foliated texture
- Foliation
- formation of orthoclase coronas or rims around leucite
- forsterite
- Forsterite (100% Mg-end member olivine)
- Forsterite Zone
- Forsteritic composition
- Forsteritic olivine
- fossil leaves
- fossil plants
- Fossiliferous
- Fossiliferous Limestone
- Fossiliferous Outcrop
- Fossiliferous shale
- Frac sand
- Frac sand source
- Fractional crystallization
- fracture filling
- fragmental texture
- Franciscan Complex
- Franconia Sandstone
- Franklin District
- Franklin Mining District
- Franklinite
- fresh surface
- fresh vs weathered rock surfaces
- frothy
- frothy texture
- gabbro
- Gabbro-Anorthosite Contact
- Galena Group
- Galena Limestone
- Garnet
- Garnet (Almandine)
- Garnet Alteration
- Garnet Clinopyroxenite
- garnet fracturing
- garnet granite
- Garnet Inclusions
- garnet omphacite assemblage
- Garnet porphyroblast
- Garnet pyroxenite
- Garnet schist
- Garnet sillimanite schist
- garnet staurolite cummingtonite schist
- Garnet-rich sandstone
- Garnet-Staurolite Schist
- Garnet–staurolite schist
- Gas escape structures
- Gastropods
- Geochemical environment indicator
- Geochemical Weathering
- geological education
- geomicrobiology
- geomorphology
- Geomorphology of Ethiopia
- Germany
- Giants Range Batholith
- Gibbsite
- Gienah Gurab Escarpment
- glacial deposits
- glacial diamictite
- glacial erratic
- Glacial Potholes
- glacial transport
- glaciogenic sediment
- Glaciogenic slate
- glaciomarine deposits
- Glass
- Glass sand
- Glass shard morphology
- Glass shard-rich ash
- glass shards
- glassy fiber
- Glassy groundmass
- glassy ignimbrite
- Glassy Texture
- Glauconite
- Glauconite cement
- Glauconite-bearing Sandstone
- Glauconitic sandstone
- Glaucophane
- Glaucophane schist
- Glenwood Formation
- Glenwood Shale
- global glaciation
- Glomerocryst
- glomerocrysts
- Glomeroporphyritic
- glomeroporphyritic plagioclase
- Glossopteris
- gneiss
- Goethite
- goethite alteration
- Golding-Keene
- Gondwana
- Goodhue County
- Grain Boundary Migration
- Grain size variation
- Grand Canyon Geology
- Grand Canyon stratigraphy
- Grand Canyon Supergroup
- Grand Canyon Volcanism
- granets
- granite
- Granite Falls
- Granite Falls Geology
- Granite Falls Minnesota
- granite host rock
- Granite Pegmatite
- Granite–andesite interaction
- Granitic Differentiation
- Granitic Protolith
- granitic xenoliths
- granitoid
- granodiorite
- Granodiorite Transition
- granular texture
- granulite
- granulite facies
- Graphic granite
- Graphic Texture
- Graphite
- Great Cambrian Transgression
- Great Unconformity
- Greece Metamorphic Terrane
- Green River Formation
- Green Sand Beach
- green schist
- Greenschist facies
- Greenstone belt rock
- Grenville Province
- grid twining
- Grid twinning
- grid-like twinning
- Grinding Stone Material
- Grinding stone technology
- Grossular Garnet
- Groundmass
- groundwater discharge
- Groundwater flow
- Groundwater interaction
- Groundwater-rock interaction
- Growth twinning
- Growth Zoning
- Grunerite
- Gunnison County Geology
- gypsum plate
- Hadar
- Hakata Shale
- Hakatai Shale
- hand sample
- Harney Peak Granite
- harzburgite
- Harzburigte
- hauyne
- Hauyne-bearing basanite
- Hawaiʻi
- Hawaii
- Hawaii Big Island
- Hawaii field trip
- Hawaii Geology
- Hawaii Island
- Hawaii volcanic rocks
- Hawaii volcanism
- Hawaiian basalt
- Hawaiian eruption
- Hawaiian hotspot
- Hawaiian hotspot volcanism
- Hawaiian volcanism
- Hawaiian Volcanoes
- Hawaiite
- Hematite
- hematite alteration
- Hematite Cement
- Herzolite
- Hibbing Mine
- high birefringence
- High K₂O content
- High Perovskite Content
- High refractive index mineral
- high relief
- High-energy depositional environment
- high-energy environment
- high-grade metamorphic
- High-Grade Metamorphic Rock
- high-grade metamorphism
- High-Mg volcanic rock
- High-Pressure Metamorphism
- High-purity quartz sand
- High-silica rhyolite
- High-temperature lava
- High-Ti pyroxene
- higher-order colors
- highly weathered
- Himalaya
- Himalayan metamorphism
- Hinckley Sandstone
- Holocene deposits
- Hominin archaeology
- Hominin behavior
- Horn of Africa archaeology
- Hornblende
- hornblende dehydration
- Hornblende gabbro
- hornblende mantle
- Hornblende pleochroism
- Hornblende Quartz Schist
- Hornfels Facies
- hornito
- Hotspot Volcanism
- HOV Alvin
- Hualālai Volcano
- Hybrid Magma
- Hybrid rock
- hybridization
- Hydration Reaction
- Hydraulic fracturing
- Hydraulic fracturing sand
- Hydrological recharge
- Hydrolysis
- hydrothermal
- Hydrothermal alteration
- hydrothermal breccia
- hydrothermal fluids
- hydrothermal mineral
- Hydrothermal minerals
- Hydrous Alteration
- hydrous magma
- Hydrous Magmatism
- Hydrous Minerals
- Hydrous Phase Reaction
- Hypersthene
- Ibex Hills
- ice age
- iceberg rafting
- Iddingsite
- Iddingsite (alteration product)
- Idlewild Member
- igneous
- Igneous Contact
- igneous mineral reaction
- Igneous mineral zoning
- Igneous petrology
- igneous rock classification
- Igneous Rocks
- Igneous Texture
- igneous textures
- ignimbrite
- ijolite
- Ilmenite
- Immature sandstone
- Immature sediment
- Immature Texture
- Immobile Element Concentration
- inclusion
- inclusion in garnet
- incongruent melting
- Index Mineral
- index minerals
- India-Asia collision
- Ingersoll Mine
- inosilicate
- interconnected vesicles
- Intercumulus Melt
- Interference Colors
- interference figure
- Interference figures
- interference rings
- interlocking texture
- intermediate
- Intermediate composition
- Intermediate Igneous Rock
- Intermediate Lava
- Intermediate Magma
- Intermediate volcanic rock
- Interstate State Park
- interstitial
- Interstitial Melt
- Interstitial plagioclase
- Interstitial pyroxene
- interstitial pyroxenes and oxides
- Interstitial Texture
- Intrusion–host contact
- Intrusive alkaline complex
- Intrusive Carbonatite Complex
- intrusive contact
- Intrusive Dome Complex
- Intrusive felsic rock
- Intrusive igneous petrology
- Intrusive igneous rock
- Intrusive Rock
- Intrusive texture
- Inverted Topography
- Iowa
- iron carbonate
- iron formation
- Iron Hill
- Iron Hill Carbonatite
- iron ore mineral
- iron oxidation
- iron oxide alteration
- iron oxide bands
- Iron oxide cement
- Iron Oxide Coating
- iron oxide intergrowth
- Iron Oxide Replacement
- Iron oxide staining
- Iron Oxides
- iron oxyhydroxide
- Iron-rich bands
- iron-rich groundwater
- Iron-Titanium Oxides
- Isochrome
- Isochromes
- isochrons
- Isogyre
- isogyre behavior
- isogyre movement
- Isogyres
- Isotropic crystals
- Isotropic mineral
- isotropic mineral (perovskite in XPL)
- Isotropic minerals
- Istotropic hauyne
- Italy
- Italy geology
- IUGS classification
- Jack Hills
- Jacobsville Sandstone
- jasper
- Johnson Shut-Ins Rhyolite
- Jones Pit
- Jordan Sandstone
- Jordan Sandstone Aquifer
- Jurupa Valley
- kaersutite
- KAlSi₂O₆ - KAlSi₃O₈– SiO2 system
- Kaolinite
- Keren Eritrea
- Keweenawan Supergroup
- Keystone South Dakota
- Keystone South Dakota geology
- Kilauea
- Kimberlite
- kimberlite pipe
- Kingston Peak Formation
- kink bands
- komatiite
- Koobi For a
- Korath
- Korath Range
- Kyanite
- Kyanite quartzite
- kyanite schist
- lacustrine limestone
- lahar
- lahar deposit
- lahar deposits
- lake deposits
- Lake Superior geology
- laminated limestone
- Laminated shale
- laminated siltstone
- Lamproite
- lapilli
- Lapilli formation
- large 2V
- Large Crystals
- large-format thin section
- Late Pleistocene
- Late-Stage Magmatic Fluids
- Late-Stage Magmatism
- late-stage oxidation
- Laurentide Ice Sheet
- Lava Creek A
- Lava Creek B Ash
- Lava Creek Tuff
- lava fields
- Lava flow from Kenya
- lava fountain
- Lava fountaining products
- lava morphology
- lava rampart
- lava-waffle
- layered cumulate texture
- Layered intrusion
- Layered Intrusions
- Layered mafic intrusion
- Layered Texture
- Leaching
- Lead South Dakota
- length fast
- length slow
- length slow / length fast
- leucite
- leucite alteration
- leucite and quartz
- Leucite Hills
- leucite instability
- leucite phenocryst
- leucite phonolite
- leucite phonolite.
- leucite reaction rim
- leucite replacement
- leucite stability
- leucite to orthoclase
- Leucite twinning
- leucite–orthoclase–quartz system
- Leucitite
- Leucitophyre
- Leucosome Veins
- Lherzolite
- limestone
- limestone protolith
- Limited diagenesis
- limonite
- lithic clasts
- Lithic Fragments
- Lithic technology
- lithic tuff
- Lithograph City Formation
- Lithographic limestone
- lithography
- Lithospheric Mantle
- Little Amnicon Falls
- Little Cottonwood Mining District
- Little Elk Creek Trail
- Lomekwi
- long amphibole crystals
- Longest Kenyan Lava Flow
- Longest Lava Flow
- loss of interference colors
- Low birefringence
- Low relief
- Low transport distance
- Low- to Medium-Grade Metamorphism
- Low-grade metamorphism
- Low-grade metamorphism indicator
- Low-temperature alteration minerals
- Low-Temperature Metamorphism
- Low-temperature mineralization
- lower crust
- Lower East Rift Zone
- Lower Ordovician
- LREE enrichment
- Ludwigite
- Madagascar
- mafic
- Mafic clot
- Mafic Composition
- mafic differentiation
- mafic dike
- mafic enclave
- mafic geochemistry
- Mafic Gneiss
- Mafic Igneous Petrology
- Mafic igneous rock
- Mafic intrusion
- Mafic intrusive
- Mafic Intrusive Rock
- Mafic layered intrusion
- mafic magma
- Mafic Magma Evolution
- Mafic Metamorphism
- mafic minerals
- mafic protolith
- mafic rock
- mafic sill
- mafic volcanic rock
- Mafic-derived sediment
- Mafic-ultramafic cumulate
- Mafic-ultramafic intrusion
- Mafic-Ultramafic Rock
- magma chamber processes
- Magma crystallization sequence
- magma dynamics
- magma evolution
- magma flow texture
- magma interaction
- Magma mingling
- Magma mixing
- magma recharge
- magma-mingled andesite
- Magma-Mingled Granodiorite
- magma-mingled quartz diorite
- Magmatic Differentiation
- magmatic disequilibrium
- Magmatic flow fabric
- Magmatic hybridization
- Magnesium-rich lava
- Magnesium-Rich Metamorphism
- Magnetite
- Magnetite (alteration product)
- Mai Kenetal
- Mana Flow
- mantle derived
- mantle minerals
- Mantle Petrology
- Mantle Plume
- mantle plume volcanism
- mantle residue
- mantle rock
- mantle xenolith
- mantle-derived magma
- Mantle-derived Rock
- marble
- Marble-Hosted Mineral
- Marine
- Marine transgression
- Marinoan glaciation
- Marquette
- martite
- Mary Ellen Mine
- massive perovskite crystals
- Matheos Formation
- Mathois Formation
- matrix-supported
- Mature sandstone
- Mauna Kea
- Mauna Loa
- Mechanical twinning
- Medium- to high-grade metamorphism
- medium-grade metamorphic rock
- Medium-grade metamorphism
- megacrystic
- megacrystic amphibole
- melatop
- Melatope
- melilite
- Melka Kunture
- Melt Inclusions
- Memorial Park outcrop
- Mendocino County California
- Mesabi Iron Range
- Mesabi Range
- Mesh Texture
- mesocumulate
- Mesocumulates
- Mesoproterozoic
- Mesoproterozoic geology
- meta-carbonate
- Metagabbro
- Metamict
- Metamict Texture
- Metamict Zircon
- metamictization
- metamorphic
- Metamorphic Aureole
- Metamorphic carbonate
- Metamorphic Foliation
- Metamorphic Index Mineral
- metamorphic petrology
- Metamorphic Progression
- Metamorphic provenance
- metamorphic rock
- Metamorphic Texture
- Metamorphic Textures
- Metamorphosed Mafic Rock
- Metamorphosed Quartz Sandstone
- Metamorphosed shale
- Metapelite
- metasedimentary
- Metasedimentary rock
- metasomatic
- metasomatism
- metavolcanic
- Mg olivine
- Mg rich olivine
- Mg2SiO4
- Mica fish
- Mica plate
- Mica plate insertion
- Mica Plate Test
- Micaceous Texture
- Michel-Lévy colors
- Michel-Lévy method
- Michigan geology
- Micrite
- Micritic limestone
- microbial community
- microbial mat
- microcline
- microcrystalline quartz
- Microcrystalline silica
- Microlites
- Microlitic Groundmass
- microlitic texture
- microscopic textures
- Microspar
- Mid-Oceanic Ridge Basalt
- Midcontinent Geological Province
- Midcontinent Rift
- Middle Awash
- Middle Ordovician
- Migmatite
- Migmatitic Gneiss
- Mile 222 Campground
- Mill Street
- Mineral alignment
- Mineral banding in vesicles
- Mineral inclusions
- Mineral paragenesis in cavities
- mineral precipitation
- mineral reaction
- Mineral Reaction Rim
- mineral reaction texture
- mineral replacement
- Mineral Stability
- mineralizing fluids
- mineralogy
- Mineralogy Tags
- Minnelusa Formation
- Minnesota
- Minnesota geology
- Minnesota Rive Valley
- Minnesota Rive Valley Geology
- Minnesota River Valley
- Minnesota River Valley Subprovince
- Minnesota Sogn Valley Lucille Baker-Stahl
- Minnesota Stratigraphy
- Minnesotaite
- Minor Minerals
- Miocene
- Missouri
- Missouri geology
- Mixed igneous textures
- Mn(OH)2
- MnO2
- modern-day Aswan
- Moist eruption column
- Mojave Desert
- Molar tooth structure
- molten lava blobs
- monazite
- Monsoonal activity
- Montana geology
- Montevideo Gneiss
- Monticellite
- Monumental Stonework
- monzogranite
- Moody Nunatak
- MORB
- Morton
- Morton Gneiss
- Mosaic Canyon
- Mount Pinatubo
- Mount Simon Sandstone
- Mount Simon Sandstone Equivalent
- Mt Shasta
- Muav Limestone
- mudstone
- mudstone metamorphism
- Mugearite
- Multi-stadial growth
- Multiple Intrusion
- Munro Township
- muscovite
- Muscovite to chlorite alteration Musvoite
- muscovite. Metamorphic textures
- mylonite
- myrmekite
- myrmekite-like texture
- myrmekitic texture
- Na-bearing amphibole
- NaAlSi2O6
- Naches Valley
- Nachukwi
- Native Hawaiian obsidian tools
- Negash Synclinorium
- Neoarchean
- Neoproterozoic
- Neoproterozoic basin evolution
- Neoproterozoic Earth history
- Nepal
- Nepheline
- Nepheline optic axis figure
- nepheline optics
- nepheline pegmatite
- nepheline phonolite
- nepheline syenite
- Nepheline syenite family
- Nepheline syenite suite
- Nepheline vs quartz identification
- nepheline-bearing diorite
- Nepheline-bearing rock
- Nepheline-rich rock
- New Mexico
- New World Mining District
- Newest oceanic crust sample
- Ni-Cu-PGE mineralization
- nickel
- nickel copper deposits
- Nickel Lake
- Nickel mineralization
- no concave convex isogyre
- Nodular Chert
- nonconformity
- Noonday Dolomite
- Nopeming Sandstone
- North Carolina
- North Shore Volcanic Group
- North Shore Volcanics
- Northeastern Minnesota
- northern Arizona
- Northern Arizona Volcanism
- Northern Ethiopia
- Northern Minnesota
- Northern Minnesota Geology
- Northfield
- nuée ardente
- obsidian
- Obtuse Bisectrix Figure
- Ocean Island Basalt
- Ocean island basalt (OIB)
- Oceanic crust
- Oceanic plateau
- Off-centered interference figure
- off-centered optic axis figure
- OIB
- oikocryst
- Ol-Opx-Cpx classification
- oldest minerals
- Oldowan and Acheulean Industries
- Oldowan tools
- Olduvai
- Olduvai Gorge
- Oligocene
- olivine
- Olivine alteration
- Olivine Basalt
- Olivine Crystallization
- Olivine Gabbro
- olivine peridotite
- Olivine phenocrysts
- Olivine Pseudomorphs
- olivine rimmed by orthopyroxene
- Olivine to iddingsite
- Olivine to magnetite
- Olivine to serpentine
- Olivine-Bearing Gabbro
- olivine-rich rock
- Ololosokwan
- Omo
- Omphacite
- Oneota Dolostone
- Ontario
- Ooids
- oolite
- Oolitic limestone
- Opaque oxides
- Open-Space Filling
- ophitic texture
- optic axes
- Optic Axis
- optic axis determination
- optic axis figure
- Optic Axis Interference Figure
- Optic axis Uniaxial interference figure
- Optic Sign
- optic sign negative
- optical
- optical axis (c-axis)
- optical mineralogy
- optical sign colors
- Optical sign determination
- optical sign test
- Optical zoning
- Optically negative
- optically neutral orientation
- Optically positive
- Ordovician Stratigraphy
- Ore Deposits
- Orendite
- Organic reduction
- Organic-rich limestone
- Orienta Sandstone
- Ortho-pyroxenite
- orthoclase
- orthoclase corona
- orthoclase reaction rim
- Orthopyroxene
- Orthopyroxene (OPX)
- Orthopyroxene Corona
- Orthopyroxene host
- Orthopyroxene Replacement
- orthopyroxenite
- orthorhombic leucite
- orthorhombic symmetry
- Oscillatory Zoning
- oxidation
- Oxidation (outer rim)
- Oxidation of olivine
- Oxide
- oxide exsolution texture
- oxide intergrowth
- Oxide minerals
- oxide rims
- Oxides
- Ozark Plateau
- P-T-path
- Pahrump Group
- Paleoanthropological Sites
- Paleoanthropology
- Paleoanthropology Context
- paleoclimate
- Paleoclimate proxy
- Paleoenvironments
- Paleoproterozoic
- Paleoproterozoic sedimentary rocks
- Paleosaprolite
- Pan-African Orogeny
- Papakōlea
- parasitic cones
- partial alteration
- Partial melting
- Partial Melting Features
- Patch Perthite
- patchy zoning
- pegmatite
- Pegmatite Formation
- Pegmatite texture
- pegmatitic diorite
- Pegmatitic Texture
- Pele's hair
- Pele’s Hair
- Pele’s Tears
- pelitic
- pelitic metamorphic rock (possible)
- pelitic protolith
- pelitic rocks
- Peninsular Ranges Batholith
- Penninite
- Pennsylvanian–Permian
- Penokean Orogeny
- Peralkaline igneous rock
- peralkaline phonolite
- peralkaline rocks
- peraluminous granite
- Periclase
- peridotite
- peridotite reaction zone
- peridotite suite
- peritectic reaction
- peritectic systems
- peritectic/incongruent melting
- Permian Period
- Perovskite
- perovskite highest relief minerals
- Perovskite-rich
- Perthite
- Perthite texture
- Petaca
- Petrogenesis of ijolite
- petrographic microscope
- petrographic textures
- Petrography
- Phaneritic texture
- phase diagram
- Phase diagram modeling
- Phase Equilibria
- Phase transition
- phenocryst
- Phenocrysts
- phenocrysts in alkalic volcanic rocks
- Philippines
- Phlogopite
- phonolite
- Phonolitic Dike
- phonolitic porphyry
- phonolitic rock
- Phreatomagmatic
- Phreatomagmatic eruption indicators
- phyllite
- Phyllite texture
- phyllitic quartzite
- Phyllitic Subunit
- Pillow basalt
- Pillow lava formation
- pilotaxitic texture
- pink granite
- Pipe vesicles
- Plagioclase
- Plagioclase (sodic)
- Plagioclase Accumulation
- plagioclase alignment
- plagioclase alteration
- Plagioclase feldspar
- Plagioclase laths
- plagioclase microlites
- plagioclase phenocrysts
- Plagioclase twinning
- Plagioclase-enclosed pyroxene
- Plagioclase-Pyroxene System
- plaid twinning
- plane polarized light
- plate tectonics
- platinum group elements
- Platinum-group elements (PGE)
- Platteville Formation
- Platteville Limestone
- Pleistocene climate
- Pleistocene glaciation
- Pleistocene tephra
- pleochroic amphibole
- Pleochroic halo
- pleochroic halo in biotite
- Pleochroic Minerals
- Pleochroic titanaugite
- Pleochroism
- Pleochroism (blue to lavender)
- Pleochroism (green
- Plinian eruption
- Pliocene–Pleistocene stratigraphy
- plutonic
- Plutonic Igneous Rock
- plutonic rock
- plutonic rocks
- poikilitic texture
- Poikiloblastic garnet
- Polarized Light Microscopy
- polymorphs
- polysynthetic twining
- polysynthetic twinning
- poorly sorted
- porous volcanic glass
- porphyritic
- Porphyritic basalt
- porphyritic texture
- porphyritic volcanic rock
- Porphyroblast
- porphyroblastic
- Porphyroblastic texture
- Porphyroblasts
- porphyry
- Positive Europium Anomaly
- Post-eruption fluid activity
- Post-eruption mineralization
- Post-Kinematic Garnet
- Post-kinematic growth
- Post-Magmatic Mineralization
- post-penokean
- Post-volcanic fluid circulation
- Post-volcanic mineral evolution
- Post-volcanic processes
- potassic alkaline magma
- Potassic syenite
- Potassic to Ultrapotassic
- potassic volcanic rock
- Potassium Feldspar
- Potassium Loss
- potassium-rich magma
- Powderhorn Complex
- PPL
- Prairie du Chien Group
- Pre-kinematic chloritoid
- Pre-Kinematic Garnet
- pre-kinematic granets
- Pre-Tectonic
- Pre-tectonic Garnet
- Precambrian
- Precambrian carbonates
- Precambrian stratigraphy
- prehistoric tools
- Presque Isle Peridotite
- pressure-temperature history
- printing stone
- printmaking
- Prismatic
- Prismatic crystals
- Prismatic Grains
- Prismatic Sillimanite
- Prismatic texture
- Prismatic Tremolite
- Prograde Metamorphism
- Proppant sandstone
- proterozoic
- Proterozoic Geology
- Proterozoic granite
- Proterozoic magmatism
- Proterozoic Overprinting
- Proterozoic quartzite
- Proterozoic sedimentary rocks
- Proterozoic sedimentary structures
- Protolith dolostone
- Protolith limestone
- Provenance
- Provenance & Source Rock
- Proximal deposition
- pseudo isotropic mineral
- pseudo isotropic perovskite
- pseudo-isotropic
- Pseudo-isotropic behavior
- pseudo-isotropic texture
- pseudo-leucite
- pseudoisotropic
- pseudoisotropic behavior
- Pseudoisotropic leucite
- Pseudoleucite alteration
- Pseudoleucite texture
- Pseudomorph
- Pseudomorphism
- Pseudomorphs of olivine
- Puʻu Waʻawaʻa
- pumice
- pumice-rich
- Pumpkin Spring Pool
- Purple spot
- Puu Waa Waa
- Pyrite
- Pyrochlore
- pyroclastic
- pyroclastic cone
- Pyroclastic deposit
- Pyroclastic deposits
- Pyroclastic droplets
- pyroclastic flow
- pyroclastic flow deposits
- pyroclastic rock
- pyroclastic rocks
- Pyrolusite
- pyrophyllite
- Pyroxene
- Pyroxene alteration
- Pyroxene Cleavage
- Pyroxene cleavage (90°)
- Pyroxene exsolution
- Pyroxene hydration
- pyroxene microlites
- Pyroxene pleochroism
- Pyroxene replacement
- Pyroxene Stability
- Pyroxene with anomalous interference colors
- Pyroxene zoning
- Pyroxenite
- Pyroxenite cumulate
- Quartz
- Quartz arenite
- Quartz cut perpendicular to c-axis
- Quartz Diorite
- Quartz Inclusions
- Quartz incompatibility
- Quartz interference figures
- Quartz mantled by amphibole
- Quartz optical properties
- Quartz Overgrowth
- Quartz Phenocrysts
- quartz recrystallization
- quartz resorption
- Quartz syenite
- quartz vs nepheline
- Quartz Wedge
- Quartz Wedge Test
- Quartz-Feldspar Eutectic
- Quartz-feldspar intergrowth
- Quartz-free syenite
- Quartz-K-feldspar-Plagioclase-Biotite
- Quartz-rich
- Quartz-rich Sandstone
- quartzite
- Quartzite flake tools
- Quartzite hand axe
- Quartzite Metamorphic Rock
- Quartzite Tool Use
- Quartzite toolstone
- quenched glass
- Quenched margin
- Quenched silicate melt
- quenching
- radial fracture texture
- Radial zeolite
- Radiating aggregates
- Radiating Crystals
- Radiation damage
- Radiation Damage in Zircon
- Radiation halos
- Radioactive accessory minerals
- Radioactive Waste Test Site
- Rapid quenching
- Rare Earth Carbonatite
- Rare Earth Element (REE) Enrichment
- rare earth elements
- Rare igneous rock
- rare igneous rocks
- reaction corona
- reaction rim
- Reaction rims
- reaction texture
- reaction textures
- Recrystallization
- recrystallized calcite
- Recrystallized Carbonates
- recrystallized dolostone
- Recrystallized Groundmass
- recrystallized limestone
- Recrystallized Quartz
- red
- red beds
- Red Wing
- Red Wing Geology
- Red Wing Minnesota geology
- reddish-orange coating
- redox reactions
- reducing environments
- Reduction spots
- Redwood Falls
- Redwood Falls Minnesota
- REE Geochemistry
- REE Minerals
- REE patterns
- REE-bearing minerals
- REE-bearing phases
- refractive indices
- Regional metamorphism
- Regolith
- Relict Olivine
- Relict Pyroxene
- Relict sedimentary lamination
- relief
- relief change
- replacement rims
- replacement texture
- Residual Melt Evolution
- Residual Soil
- retardation
- retardation colors
- Reticulite
- Retrograde Chlorite
- Retrograde Metamorphism
- retrogression
- rhombohedral cleavage
- rhyolite
- rhyolitic
- Rhyolitic pyroclastic deposit
- rhyolitic tuff
- rhythmic layering
- Rice County
- Riebeckite
- right-lateral fault
- Rio Grande Rise
- Riverside County
- rock collection
- Rock-water interaction
- Rockville granite
- Roman Magmatic Province
- rotating isogyre
- rounded cobbles
- Rugose coral
- Rugose Corals
- rutile
- S-type Granite
- Sacred Heart
- Sacred Heart Granite
- Salt and pepper texture
- Samre
- San Diego County geology
- San Diego Geology
- San Francisco Volcanic Field
- sandstone
- Sanidine
- sapphire geology
- saprolite
- Saprolitic Weathering
- Sarah Greene Hoffmann '05
- Saratoga Talc Mine
- Scapolite
- scenic geology
- schist
- Schist Muscovite schist Muscovite Schistose
- Schistosity
- scoria
- Seafloor alteration
- Seafloor alteration record
- Seafloor chemical processes
- Seafloor weathering
- Secondary mineral assemblage
- Secondary mineral infill
- Secondary mineral zonation
- secondary mineralization
- Secondary minerals
- Secondary sericite
- sediment provenance
- sedimentary
- Sedimentary geology
- sedimentary mineral
- Sedimentary petrology
- Sedimentary rock
- Sedimentary structure formation
- Sedimentary Structures
- Sedimentary textures
- seed ferns
- Senior Comps
- Sensitive Tint Plate
- Sequential mineral precipitation
- Sequential precipitation of minerals
- Sericite
- sericite alteration
- Sericite Separation
- Sericitic alteration
- sericitization
- Sericitization of plagioclase
- Sericitized plagioclase
- Serpentine
- Serpentine (alteration product)
- Serpentine (alteration)
- Serpentine alteration
- Serpentine Minerals
- serpentinite
- Serpentinization
- Serpentinized Olivine)
- serpentinized peridotite
- Shakopee Dolostone
- Shakopee Formation
- shale
- shale metamorphism
- Shallow Marine Deposition
- Shallow marine environment
- Shallow water eruption indicators
- shallow-marine environment
- Sheaf-like olivine
- Sheep Mountain
- Shoreline
- Shoshone
- Shoshone California ash
- Shovel Point
- Sibo Wang
- Siderite
- Siderite Carbonatite
- Silica
- silica activity
- Silica cement
- silica cemented
- Silica Depletion
- silica enrichment
- Silica overgrowth
- silica polymorph
- silica saturation
- silica undersaturated
- silica undersaturated magma
- silica undersaturated rocks
- Silica-cemented sandstone
- silica-melt interaction
- Silica-poor magma
- Silica-rich bands
- silica-undersaturated
- Silica-undersaturated igneous rock
- Silica-undersaturated intrusion
- silica-undersaturated magma
- Silica-undersaturated magmatism
- Silica-undersaturated rock
- Silica-undersaturation
- Siliceous carbonate protolith
- Siliceous Dolostone
- Silicic magma evolution
- Silicic volcanic rock
- siliciclastic
- siliciclastic sediment
- siliciclastic transition
- sill
- sillimanite
- sillimanite aggregates
- Sillimanite schist
- siltstone
- Silurian Hills
- Silver Bay
- Silver Bay Minnesota
- Silver-Lead-Zinc Veins
- Simultaneous intrusion
- Sioux Quartzite
- skarn
- Skarn Assemblage
- Skarn Formation
- skarn mineralogy
- Skeletal olivine
- Sky Blue Hill
- slate
- Slaty cleavage
- slow axis
- slow ray
- slow ray direction
- small 2V
- Small 2V angle
- Snowball Earth
- Snowball Garnet Texture
- Soda Butte Creek
- Sodalite
- Sodalite group
- Sodalite group minerals
- Sodalite syenite
- Sodic amphibole
- Sodic pyroxene
- Sodic syenite
- Sodium-rich mineral
- Sogn
- Solid solution
- Solid solution (opx–cpx)
- Solid solution series
- Solnhofen Limestone
- Solnhofen Plattenkalk
- Solvus
- Sonoma County
- South America
- South Atlantic Ocean
- South Dakota
- South Dakota geology
- southeastern Minnesota
- Southern Ethiopia
- Southern Ethiopia geology
- Southwestern Minnesota
- spatter cone
- Spatter lava
- Sphene
- Sphene (Titanite)
- Sphene high birefringence
- Spherical cavities
- spherulites
- Spherulitic Texture
- Spinel
- Spinel (euhedral)
- Spinel Lherzolite
- Spinel Peridotite
- spinifex
- Spinifex olivine
- Spinifex texture
- spinning isogyre
- Split Cinder Cone
- Split Rock Lighthouse
- spring
- St. Cloud granite
- St. Croix River Geology
- St. Francois Mountains
- St. Lawrence County Geology
- St. Peter Sandstone
- Staurolite
- Staurolite Quartzite
- Staurolite twinning
- Sterling Hill Mining District
- Stettin Pluton
- Stillwater Complex
- Stillwater Complex Petrology
- stilpnomelane
- stilpnomelane schist
- Stone tool manufacture
- straight isogyre
- stratigraphic contact
- Stratigraphic Marker
- stretched
- strike-slip faulting
- String Perthite
- Stromatic Migmatite
- stromatolite
- Stromatolites
- Strombolian eruption
- strong birefringence
- Strong Foliation
- Strontianite
- Sturtian glaciation
- stylolites
- Subarkosic Sandstone
- subduction
- Subduction complex
- Subduction zone magmatism
- Subduction zone metamorphism
- Subhedral plagioclase
- Subject Graphic Granite
- Submarine basalt
- Submarine eruption
- Submarine volcanism
- Subophitic texture
- Subsolidus
- subsolidus alteration
- Subsolidus Reaction
- Subsolidus Reaction phaneritic texture
- Subsolidus transformation
- Subtraction
- subtraction colors
- subtraction of retardation
- subtraction quadrants
- Sugary Texture
- sulfide mineralization
- Sulfide minerals
- Sulfide veins
- Sulfides
- Supereruption
- Supermature sandstone
- Supersaturation mineral growth
- Supersaturation-driven deposition
- Surface Alteration
- Sutured Grain Boundaries
- Syene
- syenite
- Symplectite
- Syn-kinematic chloritoid
- Syn-Kinematic Garnet
- Syn-kinematic growth
- Syn-Tectonic
- TagsAmphibole Alteration
- Tahiti
- Tahiti basalt
- Talc
- talc alteration
- talc deposit
- Talc Group Minerals
- talc mine
- Talc reaction
- talc tremolite schist
- Talc vs Muscovite
- Talc Zone
- Talc-bearing phyllite
- Talc-Tremolite Schist
- Talc–chlorite schist
- Tambien Group
- Tanzania
- Tanzanian Craton
- Tapeats Sandstone
- Tarlac Philippines
- tartan plaid-like patterns
- Tartan twinning
- tartarn twining
- TAS diagram
- Taylors Falls
- Taylors Falls Geology
- teaching specimens
- tectonic breccia
- tectonic stacking
- Tekeze
- Tekeze River
- tephra
- Tephra Layers
- Tephrite
- tephrites
- Tephrochronology
- Tephrostratigraphy
- ternary phase diagram example
- tetragonal leucite
- tetragonal symmetry
- Textural maturity
- Texturally mature
- thermal aureole
- Thermal Metamorphism
- thin section
- Thin Section Teaching Sample
- Tholeiitic Basalt
- Thomson Dam geology
- thread lace scoria
- Ti-rich amphibole
- Ti-rich mineral assemblage
- Ti-rich phlogopite
- Tieton Andesite
- Tigray
- Tigray Ethiopia
- Tigray geology
- Tigray Highlands
- Tigray region
- Tintic Quartzite
- Titanaugite
- Titanaugite interference colors
- Titanaugite optical properties
- Titaniferous phases
- Titanite
- Titanite (Sphene)
- Titanite interference colors
- titanium-rich phases
- Titanium-rich pyroxene
- Titanoaugite
- Tonsina
- Tonto Group
- Toolmaking traditions
- Topaz
- Total Alkali Silica diagram
- Total Alkali–Silica diagram
- Tourmaline
- trace elements
- Trace fossils
- Trachyandesite
- Trachydacite
- trachyte
- Trachytic Texture
- Traditional grinding stones
- Transantarctic Mountains
- Travertine
- Tremolite
- Tremolite Zone
- tridymite
- trilobite
- Trilobite fossils
- Trilobites
- Troctolite
- Tufa dam
- tuff
- Tuff Alteration
- tuffaceous material
- Tulu Bor Alpha Tuff
- Tunnel City Formation
- Turbidite
- Turkana Basin
- Turkana Basin tuffs
- TurkanaMuseum in Tanzania
- Twin Lamellae
- Twining
- twinned crystals
- twinned perovskite
- Twinning lamellae
- two cleavages in amphibole
- two component systems
- Two-Component System
- Uganda
- Uganda volcanics
- Uinkaret Volcanic Field
- ultra-high pressure metamorphism
- ultra-high-pressure metamorphism
- ultrabasic
- ultramafic
- ultramafic alteration
- Ultramafic chemistry
- ultramafic igneous rock
- Ultramafic rock
- Ultramafic Rocks
- Ultramafic Volcanic Rock
- Ultrapotassic composition
- Ultrapotassic volcanic rocks
- undulatory extinction
- Undulose Extinction
- Uniaxial interference figure
- uniaxial mineral
- Uniaxial Minerals
- Uniaxial negative
- Uniaxial negative interference figure
- Uniaxial negative mineral
- Uniaxial optics
- Uniaxial Positive
- United Kingdom
- Unkar Group
- unweathered surface
- Upper Black Hills
- Upper Cretaceous
- upper mantle
- Upper mantle melting
- Upper Peninsula Michigan
- USA
- Utah
- Vapor-Phase Crystallization
- Vapor-Phase Minerals
- vein
- vein mineralization
- veins
- vermicular intergrowth
- Vermicular quartz
- vermicular texture
- Vesicle alteration
- Vesicle fills
- Vesicle formation
- Vesicle formation from volcanic degassing
- Vesicle infill
- Vesicle infill minerals
- Vesicle mineralization
- Vesicle-filling processes in basalt
- Vesicle-Lining Crystals
- Vesicles
- vesicular basalt
- Vesicular Glass
- Vesicular Lava
- vesicular pumice
- vesicular texture
- Vesiculated volcanic glass
- vesiculation
- Vesuvianite
- vibration directions
- Vishnu Schist
- Vitreous Luster
- Vitric glass
- vitric tuff
- vitrophyre
- vitrophyric texture
- Volatile-Rich Melt
- volcanic
- Volcanic amphibole
- Volcanic arc
- volcanic ash
- Volcanic ash aggregation
- Volcanic Ash Alteration
- Volcanic ash correlation
- Volcanic Ash Layers
- volcanic bombs
- Volcanic Breccia
- volcanic cone
- Volcanic Degassing
- Volcanic Gas Alteration
- Volcanic Geochemistry
- Volcanic glass
- Volcanic glass cement
- Volcanic glass geochemistry
- Volcanic hailstones
- volcanic landscape
- volcanic mudflow
- volcanic outcrop
- Volcanic petrology
- Volcanic phenocrysts
- Volcanic Protoliths
- Volcanic rock
- Volcanic rock texture
- Volcanic rock with secondary mineralization
- Volcanic Rocks
- volcanic scoria
- volcanic spatter
- Volcanic tephra
- volcanic texture
- Volcanic textures
- volcaniclastic
- volcaniclastic rocks
- volcaniclastic sediment
- Volcaniclastic textures
- Volume expansion
- Wangs Corner
- Warsaw Township
- Wasatch Mountains
- Washington County Quartzite
- Wausau Intrusive Complex
- Wausau Wisconsin
- Wavy extinction
- Weathered Gneiss
- weathered surface
- Weathering
- Weathering Effects
- weathering rind
- Webster
- websterite
- Wehrlite
- welded lava fragments
- welded tuff
- welding
- Well-rounded quartz grains
- Well-sorted sandstone
- Western Alps UHP
- Western Australia
- White Cliffs
- White mica
- Willemite
- wind blown volcanic material
- Wisconsin geology
- Wisconsine
- Witherite
- Wollastonite
- Wyoming
- Wyoming geology
- Wyoming volcanics
- Wyominite
- xenolith
- xenoliths
- XPL
- Yellow colors in 1st and 3rd quadrants Addition and subtraction
- Yellow colors in 2nd and 3rd quadrantes
- yellow quadrants
- yellow subtraction
- yellow)
- Yellowstone Caldera
- Yellowstone geology
- Yellowstone volcanic system
- Zabriskie Quartzite
- Zambales
- Zeolite
- Zeolite facies alteration
- Zeolite group minerals
- Zeolites
- Zircon
- Zircon (detrital)
- zircon grains
- Zircon inclusions
- Zircon Separation
- zircon zoning
- Zirkel Mesa
- Zoned aegirine-augite
- Zoned crystals
- Zoned feldspars
- Zoned minerals
- Zoned plagioclase
- Zoned pyroxene
- Zoned pyroxenes
- Zoned secondary mineral infill
- Zoned titanaugite
- zoned tourmaline
- Zoned vesicle infill
- Zoned Zircon
- Zoning
- Zoning in pyroxenes