Transmitted Light

Mineral properties

Mineral	Colour	Birefringence	Relief	Noteworthy Features	Cleavage	Extinction	Habit	2V Angle	Optic Sign	Found In	Associated Minerals	Mineral Group	Crystal System
Actinolite Actinolite in PPL. Actinolite in XP.	Colourless to Green Pleochroic. More Green for more Fe-rich	Moderate. 0.027 up to mid 2^nd order	Moderate	C to Epidote: less Yellowish and lower relief / Length Slow	Good. 2 sets at 124°	Inclined 30° max / Typically 15°	Fine Prisms / Laths / Fibrous / Needle-like	Large 75-80°	Negative	Metamorphic (Green and Blueschist, Serpentinite, Marbles)		Actinolite Amphibole	Monoclinic
Aegirine Aegirine in PPL. Aegirine in XP.	Bright Green / Yellow / Brown / Pleochroic	High. 0.04-0.06 up to 3^rd or 4^th	High	May occur as rim on other green pyroxenes / Length Fast	Good. 2 sets at 87°	Inclined 0-10°	Needle Prisms / Hexagonal	Large 80-90°	Negative	Igneous	Albite Epidote Biotite Sphene Talc Calcite Chlorite Quartz Sericite	Clinopyroxene	Monoclinic
Aenigmatite Aenigmatite in PPL. Aenigmatite in XP.	Dark Brown to opaque / Strongly Pleochroic in very thin sections	Very High	High to Very High	Intergrowths with Arfvedsonite are common / Opaque to smoky haloes around Orthite inclusions / Polysynthetic Twinning	Good. 2 sets at 66°	Inclined 4-45°	Columns / Needles	Small to Moderate 27-55°	Positive	Igneous (Felsic, Na-rich rocks)	Anorthoclase Arfvedsonite Clinopyroxenes Nepheline	Sapphirine Supergroup	Triclinic
Akermanite	Colourless / Weakly Pleochroic	Low	Moderate	May have anomalous interference colours (Purple Blue) / Interpenetrating twinning / Length Fast	Poor. 2 sets	Straight	Plates	Uniaxial	Positive	Igneous (Silica-undersaturated Volcanic rocks) / Metamorphic	Epidote Sphene Tourmaline	Melilite	Tetragonal
Albite	Colourless	Low. up to cream	Very Low	Albite Twinning lengthways / Carlsbad Twinning / Common in low-grade Metamorphic rocks with Chlorite, Muscovite and Actinolite / May occur as rims on more calcic plagioclase later replacement of feldspars in Igneous rocks.	Perfect and Good. 2 sets at 86°	Inclined 12-20°	Prisms	Large 70-80°	Positive	Igenous / Metamorphic	Leucite Nepheline Olivine Titanaugite	Plagioclase Feldspar	Triclinic
Allanite / Orthite Allanite in PPL. Allanite in XP.	Yellow / Pink / Magenta / Deep Brown Pleochroism	Moderate to High. 0.018-0.030	High	Commonly zoned / with Epidote and Clinozoisite rims (due to radiation damage) / Rich in REE	Poor	Straight or Inclined	Irregular Prisms / Needles	Moderate to Large 40-80°	Negative	Igneous (Acid to Intermediate rocks) / Metamorphic (Low to High grade regional metamorphism)	Biotite Cordierite Quartz Sericite Muscovite	Epidote	Monoclinic
Almandine	Colourless / Reddish	Isotropic	High	Porous texture / Heliocentric inclusion spirals	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Metamorphic (Low to high grade)	Biotite Clinopyroxene Olivine Hornblende MicroclineK-Feldspar Orthopyroxene Quartz Titanaugite Volcanic Glass	Garnet	Cubic
Analcime / Analcite	Colourless	Very Weak (may be anomalous)	Low	Often in groundmass between Plagioclase grains in Dolerite and Basalt rocks / Replaces Leucite / Polysynthetic Twinning	Poor	Almost Isotropic	Euhedral / Anhedral / usually deformed / Spheres	Nearly Isotropic	Negative	Igenous (Basic volcanic rocks)	Biotite Clinopyroxene Olivine Hornblende MicroclineK-Feldspar Orthopyroxene Quartz Titanaugite Volcanic Glass	Zeolite	Triclinic / Pseudo Cubic
Anatase	Yellow Brownish / Blue / Opaque	Very High	Very High	May have zoned colour distribution / Length Fast	Perfect. 2 sets	Straight	Detrital / Granular / Needles	Uniaxial	Negative	Sedimentary		Oxide	Tetragonal
Andalusite Andalusite in PPL. Andalusite in XP.	Colourless / Red / Yellow / Green / Pale Pink Pleochroic	Low. 0.009-0.012 up to White	Moderate	May alter to Mica / Patchy Pink colouration / Graphite inclusions / Length Fast	Good	Straight	Prisms / Cubes / Needles	Large 70-90°	Negative	Metamorphic (Low-P metapelites) / rare in igneous		Al Silicate	Orthorhombic
Andesine	Colourless	Low. up to pale Gray	Very Low	Albite Twinning lengthways / Carlsbad Twinning / Often zoned / with Hornblende in Igneous rocks / Found in medium to high grade metamorphic rocks	Perfect and Good. 2 sets at 86°	Inclined 12-28°	Prisms / Tabular / Laths	Large 70-90°	Negative	Igenous / Metamorphic (Medium to High grade)	Calcite Zeolite	Plagioclase Feldspar	Triclinic
Andradite Andradite in PPL. Andradite in XP.	Green to Brown	Isotropic (may be anomalous)	Very High	Zonal growth rings / Mottled colour texture	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Metamorphic (Fe-metasomatosed skarn)	Biotite Diopside Hornblende Hypersthene Olivine Plagioclase	Garnet	Cubic
Anhydrite Anhydrite in PPL. Anhydrite in XP.	Colourless	Very Low	Very High to Moderate	Distorted cleavage planes / Alters to Gypsum with water / Polysynthetic Twinning	Good. 3 sets	Straight	Granular / Needles	Moderate to Small 42°	Positive	Sedimentary (Evaporites)	Albite Almandine Chlorite Clinopyroxene Hornblende Kyanite MuscoviteK-Feldspar Orthopyroxene Plagioclase Quartz Staurolite Volcanic Glass	Sulphate	Orthorhombic
Anorthite	Colourless	Low. up to cream / Yellow	Low	Distinctive Twinning lengthways / Often zoned: typically Anorthite (Ca-rich) centres and Albite (Na-rich) rims. Anorthite cores tend to alter to a fine-grained, turbid, white mica (Sericite) / More commonly found in very high grade metamorphic rocks than in igneous rocks	Perfect and Good. 2 sets at 86°	Inclined 52°	Prisms	Large 80-90°	Negative	Igneous / Metamorphic (High grade)	Biotite Clinopyroxene Olivine Hornblende MicroclineK-Feldspar Orthopyroxene Quartz Titanaugite Volcanic Glass	Plagioclase Feldspar	Triclinic
Anorthoclase Anorthoclase in PPL. Anorthoclase in XP.	Colourless	Very Low	Very Low to Low	Cross Hatched twinning / Length Fast	Good. 2 sets at 90°		Plates / Lath-Like / Granular	Moderate to Large 60-110°	Positive / Negative	Igneous (Na-rich Volcanic rocks)		Alkali Feldspar	Monoclinic
Anthophyllite Anthophyllite in PPL. Anthophyllite in XP.	Colourless	Low to Moderate. 0.013 up to mid 2^nd order	Moderate	Occurs in Mg-rich metamorphic rocks (e.g. low-grade metabasites) / Often with Talc / Like Actinolite but parallel extinction / Length Slow	Good. 2 sets at 124° (Amphibole Cleavage)	Straight	Prisms	Large 70-90°	Positive	Metamorphic (Low-P metapelites)	Aegirine-Augite Calcite Melanite Nepheline Sanidine Sodalites	Amphibole	Orthorhombic
Antigorite Antigorite in PPL. Antigorite in XP.	Colourless to Pale Green / Weakly Pleochroic	Very High	Low to Moderate	Fan-shaped multiple twins with undulose extinction / Grid texture in ultrabasic rocks / Length Slow	Perfect	Straight / May be Undulose	Radiating / Flaky / Long Prisms / Scaly	Small to Moderate 27-60°	Negative	Metamorphic (Low grade and Serpentinites)		Serpentine	Monoclinic
Apatite Apatite in PPL. Apatite in XP.	Colourless / Pale Red Grey or Brownish	Very Low. 0.002 Gray	Moderate	Usually as tiny elongate crystals with rounded or hexagonal outline / Often as accessory mineral / Length Fast	Poor. 2 sets	Straight	Hexagonal / Elongate Prisms / Laths / Oolitic spheres / Radiating branches	Uniaxial	Negative	Igneous / Metamorphic / Sedimentary	Albite Almandine Biotite Chlorite Quartz Rutile Sericite	Phosphate	Hexagonal
Apophyllite	Colourless	Very Low	Low		Perfect	Straight	Platy / Granular / Tabular	Uniaxial	Positive / Negative	Igneous (Fractures and Amygdules in basic Volcanic rocks)	Olivine Serpentine Titanaugite		Tetragonal
Aragonite	Colourless	Very High. 0.155	Low to High	No rhombohedral Cleavage / Simple to Lamellar twinning / Length Fast / Cavity Filling in volcanic rocks	Poor	Straight	Prisms / Radiating needles	Small 18°	Negative	Sedimentary (with organics)		Carbonate	Orthorhombic
Arfvedsonite Arfvedsonite in PPL.	Green / Purple / Brown / Dark Blue / Pleochroic	Very High / May be Anomalous	Moderate to High	Poikilitic sieve texture / Simple Twinning / Length Fast	Perfect and Good. 2 sets	Inclined 65-80°	Thick Columns / Elongate Prisms / Needles / Granular / Flaky	Small to Large 0-100°	Positive / Negative	Igneous (Nepheline Syenite)	Andalusite Biotite Garnet Hercynite Hypersthene Quartz K-Feldspar Muscovite Plagioclase Quartz Sillimanite	Alkali Amphibole	Monoclinic
Augite Group Augite in PPL. Augite in XP.	Colourless to Pale Green / Brown / Pleochroic	Moderate. 0.018	Moderate to High	Simple Twinning / May have zoned colour distribution / Relief changes depending on orientation / Alters to Amphibole, Chlorite, Epidote and Talc / Replaces Diopside in Limestones	Good. 2 sets at 87°	Inclined 35-50° / May be Undulose	Prisms / Hexagonal / Needles	Moderate 60°	Positive	Igneous (Alkaline basalts) / Metamorphic	Almandine Also Garnet Clinozoisite Epidote Jadeite Lawsonite Omphacite Pumpellyite Rutile Zoisite	Clinopyroxene	Monoclinic
Barite Barite in PPL. Barite in XP.	Colourless	Very High	Moderate	Kinking and crenulation / Polysynthetic Twinning / Length Fast	Good. 3 sets	Straight	Flaky / Granular / Fibrous / Columns / Elongate Prisms / Platy / Radial	Moderate 36-38°	Positive	Igneous / Metamorphic / Sedimentary (as gangue in hydrothermal deposits, in concretions in sandstone and in desert roses)			Orthorhombic
Barrosite Group	Blue Green / Pleochroic	Very High	Moderate to High	May have pleochroic haloes / Use associated minerals to distinguish from other amphiboles / Alters to Actinolite, Antigorite, Chlorite / Length Slow	Perfect. 2 sets at 124°	Inclined 15-22°	Short to Long Columns / Elongate Prisms / Needles	Moderate to Large 65-90°	Negative	Metamorphic (Low grade)	Augite Olivine Pigeonite Plagioclase	Green Hornblende Amphibole	Monoclinic
Beryl Beryl in PPL. Beryl in XP.	Colourless / Pale Blue to Pale Green / Weakly Pleochroic	Low	Very High to Moderate	May be anomalously Biaxial / Length Fast	Poor	Straight	Short to Long Prisms / Granular	Uniaxial	Negative	Igneous (Granite pegmatites) / Metamorphic			Hexagonal
Biotite Biotite in PPL. Biotite in XP.	Brown or Green / Pleochroic	High. 0.028	Moderate to High	Easily altered to Chlorites or Clays / More opaque in volcanic rocks / Mottled / Length Slow	Perfect	Straight or Inclined 5°	Hexagonal / Plates	Small 0-35°	Negative	Igneous / Metamorphic		Biotite Mica	Monoclinic
Bronzite	Pale Green / Weakly Pleochroic	Very High	Moderate to High	A variety of Enstatite / Zoning with Mg-rich core in Colcanic rocks / often with exsolution lamellae in Plutonic rocks / Alters to serpentine	Good. 2 sets		Short Columns / Elongate Prisms / Granular	Large to Moderate 97-63°	Positive / Negative	Igneous (Basic to ultrabasic rocks)	Hematite Quartz Topaz Tourmaline	Orthopyroxene	Orthorhombic
Bytownite	Colourless	Low. up to cream	Low	Albite Twinning lengthways / Carlsbad Twinning / Often zoned: typically Anorthite (Na-rich) centres and Albite (Ca-rich) rims. Anorthite cores tend to alter to a fine-grained, turbid, white mica (Sericite) / Often with Clinopyroxene and/or Olivine in Igenous rocks.	Perfect and Good. 2 sets at 86°	Inclined 40-52°	Rectangular Laths / Prisms	Large 80-90°	Negative	Igenous / Metamorphic (High grade)		Plagioclase Feldspar	Triclinic
Calcite Calcite in PPL. Calcite in XP.	Colourless	Very High. 0.172 Extreme pastel colours	Low to High	Twinkling Cleavage / Lamellar Twinning / Found infilling Fauna and Flora in carbonates / Length Fast	Perfect. 3 sets (Rhombohedral)	Straight	Interlocked Grains / Fibrous / Oolitic spheres	Uniaxial	Negative	Metamorphic / Sedimentary		Carbonate	Trigonal
Cancrinite Cancrinite in PPL. Cancrinite in XP.	Colourless / Pale Yellow	Moderate. 0.018	Low Negative	Often replaces Nepheline / Length Fast	Perfect	Straight	Elongate Prisms / Laths / Fibrous	Uniaxial	Negative	Igneous	Almandine Also Garnet Clinozoisite Epidote Jadeite Lawsonite Omphacite Pumpellyite Rutile Zoisite	Feldspathoid	Hexagonal
Carbon (Organic) Carbon in PPL.	Brownish to Gray / Opaque		Very Low to Very High	As a black pigment in many organic rich rocks	Not a crystal		Granular (Small)	Not a crystal	Not a crystal	Metamorphic (Low-grade) / Sedimentary (Organic rich)			Amorphous
Cassiterite Cassiterite in PPL. Cassiterite in XP.	Gray / Yellow / Red / Brown / Weakly Pleochroic	Very High	Very High	May have zoned colour distribution / Pleochroic haloes / Twinning / Length Slow	Good	Straight	Granular / Prisms / Needles	Uniaxial	Positive	Igneous (Pegmatitic Ore deposits) / Metamorphic (Greisen and contact skarn)	Clinopyroxenes Leucite Melanite Nepheline Olivine Plagioclase Volcanic Glass Sanidine Titanaugite		Tetragonal
Celadonite	Green / Pleochroic	Very High	Moderate	Pseudomorphs after Olivines / Length Slow	Pefect	Inclined 2-3°	Radiating / Fine Grained	Small 0-20°	Negative	Igneous (Cavity filling in basalts) / Metamorphic (Zeolite facies)			Monoclinic
Chabazite	Colourless	Very Low to Low	Very Low	Mostly as subgrains / Simple Twinning	Good	Straight	Cubes / Prismatic	Small 0-30°	Positive / Negative	Igneous (Cavity and Fractures Filling in Volcanic rocks, in veins in plutonic rocks)		Cubic Zeolite	Trigonal
Chalcedony Chalcedony in XP.	Colourless	Low	Very Low to Low			Straight	Needles / Radiating / Dense	Uniaxial	Positive	Igneous (Fractures and Amygdules in Volcanic rocks)	Chromite Hematite Magnetite Pentlandite Pyrite Pyrrhotite Rutile Tantalite	Framework SiO₂	Trigonal
Chlorite Group Chlorite in PPL. Chlorite in XP.	Colourless / Green	Low or Very low. up to Gray. Usually anomalous blue, purple,	Moderate	Often with Muscovite / Also as alteration product (often of biotite)	Perfect	Inclined 0-10°	Hexagonal / Plates	Small	Positive or Negative	Low-grade Metamorphic	Biotite Clinopyroxene Olivine Hornblende MicroclineK-Feldspar Orthopyroxene Quartz Titanaugite Volcanic Glass	Sheet	Monoclinic
Chlorite (Fe²⁺)	Dark Olive Green to Brown-Green / Pleochroic	Very High / May be Anomalous Blue	Moderate to High	Length Slow	Perfect	Straight (Parallel to Cleavage)	Thin to Thick Plates / Flaky / Scaly / Fibrous	Small 0-30°	Negative	Metamorphic (Low grade and Blueschist facies)	Epidote Glaucophane Lawsonite Pumpellyite	Orthochlorite Chlorite	Monoclinic
Chlorite (Mg, Fe²⁺)	Pale Green / Weakly Pleochroic	Very High / May be Anomalous Blue or Brown	Moderate		Perfect	Straight (Parallel to Cleavage)	Thin to Thick Plates / Flaky / Scaly / Fibrous	Small to Moderate 0-10° (if Positive) / 0-40° (if Negative)	Positive / Negative	Igneous (Amygdules in magmatic rocks)		Orthochlorite Chlorite	Monoclinic
Chlorite (Mg)	Colourless / Greenish / Weakly Pleochroic	Very High / May be Anomalous Blue	Very High to Moderate	Anomalous birefringence for Pennine, normal for Clinochlore	Perfect	Straight (Parallel to Cleavage)	Thin to Thick Plates / Flaky / Scaly / Fibrous	Small 0-30° (if Positive) / 0-5° (if Negative)	Positive / Negative	Igneous (Ultrabasic rocks, palaeo-rhyolites and acidic plutonic rocks)	Almandine Biotite K-Feldspar Muscovite Plagioclase Quartz Staurolite	Orthochlorite Chlorite	Monoclinic
Chloritoid Chloritoid in PPL. Chloritoid in XP.	Colourless / Green or Gray Blue Pleochroic	Low	High	Cleavage not as good as Mica / Twinning / Hourglass texture	Perfect. 2 sets	Almost Straight	Prisms / Euhedral / Spherical	Moderate 36-70°	Positive	Metamorphic (Low Grade)	Albite Glaucophane Jadeite Pumpellyite	Garnet	Monoclinic / Triclinic
Chromite Chromite in PPL. Chromite in XP.	Reddish / Deep Brown / almost Opaque	Isotropic if translucent	Very High	Simple Twinning	None	Isotropic	Cubes / Octahedral / Small grains	Isotropic	Isotropic	Igneous (Mafic and Ultramafic)	Clinopyroxenes Melanite Nepheline Olivine Sodalites Volcanic Glass / Never With Quartz	Oxide / Spinel	Cubic
Chrysotile / White Asbestos	Colourless to Pale Green / Weakly Pleochroic	Very Low	Low to Very High	Asbestos forming in fractures		Straight	Fibrous / Radiating	Small to Large 10-90° (if Positive) / 30-35° (if Negative)	Positive / Negative	Metamorphic (Hydrothermally altered ultrabasic and basic rocks and Greenschist Facies)	Bornite Chalcopyrite Galena Ilmenite Pentlandite Pyrite Pyrrhotite Sphalerite	Serpentine	Monoclinic
Clinozoisite	Colourless	Low to Moderate. 0.004-0.015 Anomalous	Moderate	Anomalous steel-blue birefringence	Good	Straight parallel to side / Inclined to cleavage	Prisms	Moderate to Large 40-90°	Positive	Metamorphic (Low to High grade regional metamorphism, Contact Metamorphism, Blueschist)	Biotite Hornblende MuscoviteK-Feldspar Plagioclase Quartz	Epidote	Monoclinic
Cordierite Cordierite in PPL. Cordierite in XP.	Colourless	Low. 0.008 up to White	Low	Often Spongy, Porous / may alter to yellow Pinite along cracks and margins / Twinning / Yellow pleochroic haloes around radioactive inclusions / Inclusions of Biotite and Quartz or Graphite in metamorphic rocks	Poor	Straight	Irregular / Hexagonal / Spongy	Moderate to Large 35-80°	Negative	Metamorphic (Low-P metapelites) / rare in igneous	Albite Almandine Biotite Quartz Chlorite Kyanite MicroclineK-Feldspar Plagioclase Quartz Staurolite	Ring Silicate	Orthorhombic
Corundum Corundum in PPL. Corundum in XP.	Colourless to Reddish or Blue / Pleochroic	Low (up to 1^st order Yellow)	High	May have zoned colour distribution with pleochroism / Lamellar Twinning / Length Fast	Good. 2 sets at 94°	Straight	Plates / Hexagonal / Needles / Prisms	Uniaxial	Negative	Metamorphic (Al-rich and silica-poor contact metamorphism, regional Schists)	Aegirine-Augite Apatite Leucite Melanite Melilite Olivine Sodalites Titanaugite / Never With Quartz		Trigonal
Cristobalite	Colourless	Very Low to Low	Very Low	Lamellar Twinning / Occurs in cavities in Si-oversaturated igneous rocks / Devitrification product in high T metamorphic rocks (Sanidine facies)		Straight	Plates / Spherulitic / Needles / Chalcedony-Like /Tabular Prisms / Fibrous	Uniaxial or Biaxial Small 2V (25°)	Uniaxial Positive / Biaxial Negative	Igneous (Fractures of acidic to intermediate Volcanic rocks) / Metamorphic (Sanidinite facies Contact metamorphism)	Clinopyroxenes Leucite Melanite Nepheline Olivine Plagioclase Volcanic Glass Sanidine Titanaugite	Framework SiO₂	Pseudo Cubic
Crossite	Pale Yellow / Purple / Blue / Pleochroic	Moderate. 0.02	Moderate	May be zoned	Good. 2 sets at 124°	Inclined 5-10°	Prisms / Fibrous	Small to Moderate 0-50°	Negative	Metamorphic (Glaucophane Schist, Eclogite)	Chromite Clino And Orthopyroxenes Plagioclase Serpentine	Alkali Amphibole	Monoclinic
Cummingtonite	Colourless to Pale Brown	Moderate to High. 0.02-0.045	Moderate to High	Lamellar Twinning	Good. 2 sets at 124° (Amphibole Cleavage)	Inclined 10-20°	Prisms	Moderate to Large 60-85°	Positive or Negative	Metamorphic / rare in igneous	Rutile Garnet Kyanite Zoisite	Amphibole	Monoclinic
Diopside Diopside in PPL. Diopside in XP.	Colourless / Pale Brownish / Greenish	Moderate to High. up to upper 2^nd order	High	Rare Simple Twinning / Exsolution Lamellae in Orthopyroxene / Alters to Amphibole and Serpentine	Good. 2 sets at 90°	Inclined 35-50°	Prisms	Moderate 50-70°	Positive	Igenous (Basic rocks, Kimberlites) / Metamorphic (Marbles, High grade metabasite)	Biotite Hornblende Microcline Plagioclase Quartz Sericite Sphene	Clinopyroxene	Monoclinic
Dolomite Dolomite in XP.	Colourless / Brown tinged	Very High. 0.179	Low to High	Lamellar Twinning / Commonly iron-oxide dusted / Coarser Lamellae than Calcite / Length Fast	Perfect	Inclined to Cleavage	Prisms	Uniaxial	Negative	Metamorphic / Sedimentary		Carbonate	Trigonal
Enstatite	Colourless / Weakly Pleochroic	Very Low	Moderate to High	Zoning with Mg-rich core in Colcanic rocks / often with exsolution lamellae in Plutonic rocks / Alters to serpentine	Good. 2 sets	Straight	Short Columns / Elongate Prisms / Granular	Moderate to Large 54-83°	Positive	Igneous (Basic to ultrabasic rocks)		Orthopyroxene	Orthorhombic
Epidote Epidote in PPL. Epidote in XP.	Colourless, Yellow or Greenish / Pleochroic Yellow Orange to Red Purple	Moderate to High. 0.015-0.05 up to 3^rd order / May be Anomalous	High	Occurs as accessory mineral in granitic rocks	Good	Straight or Inclined	Prisms / Granular / Hexagonal / Radiating	Moderate Large 60-90°	Positive or Negative	Metamorphic (Low-Grade metabasalts, Blueschist, Contact Metamorphism)	Leucite Magnetite Melilite Nepheline Sodalites / Never Ilmenite	Epidote	Monoclinic
Epistilbite	Colourless	Very Low	Very Low	High birefringence compared to other zeolites / Simple Twinning / Length Slow		Inclined 10°	Radial / Fibrous Aggregates / Laths	Moderate to Small 44°	Positive	Metamorphic (Hydrothermal Amygdules in Basalts and Andesites)	Albite Almandine Biotite Quartz Chlorite Kyanite MicroclineK-Feldspar Plagioclase Quartz Staurolite	Flaky Zeolite	Monoclinic
Fluorite Fluorite in PPL. Fluorite in XP.	Colourless / Blueish / Purple	Isotropic	Very High Negative	Often purple due to radiation damage / Occurs as cement in sandstones / Zonal growth rings / Mottled colour texture / Found in Hydrothermal veins	Perfect. 3 sets at 60°/ 2 Sets at 70	Isotropic	Cubes / Octahedral / Typically Massive	Isotropic	Isotropic	Igenous / Sedimentary	Calcite Diopside Leucite Melilite Nepheline Olivine Pyrope	Fluorite	Cubic
Garnet Group Garnet in PPL. Garnet in XP.	Colourless to Pale Pink (most common)	Isotropic	High	May be zoned / May have trails with Quartz and Biotite inclusions, which may have S or Z shapes / May alter to chlorite	None	Isotropic	Hexagonal / Octogonal	Isotropic	Isotropic	Metamorphic / rare in igneous		Garnet	Cubic
Gedrite Gedrite in PPL. Gedrite in XP.	Colourless	Low to Moderate. 0.013	Moderate		Good. 2 sets at 124° (Amphibole Cleavage)	Straight	Prisms	Large	Positive	Metamorphic	Clinopyroxenes Leucite Nepheline Olivine Plagioclase Sodalites	Amphibole	Orthorhombic
Gehlenite	Colourless / Yellow / Weakly Pleochroic	Low / May be anomalous Purple Blue	Moderate	Interpenetrating twinning / Length Slow	Poor. 2 sets	Straight	Short Prisms / Granular	Uniaxial	Negative	Igneous (Silica-undersaturated Volcanic rocks) / Metamorphic	Biotite Clinopyroxene Olivine Hornblende MicroclineK-Feldspar Orthopyroxene Quartz Titanaugite Volcanic Glass	Melilite	Tetragonal
Glauconite Glauconite in PPL. Glauconite in XP.	Green / Pleochroic	Very High	Moderate	Never as oolite (as opposed to chamosite) / Length Slow	Pefect	Inclined 2-3°	Spheres / Elliptic	Small 0-20°	Negative	Metmorphic (Marbles) / Sedimentary (Sandstones)			Monoclinic
Glaucophane Glaucophane in PPL. Glaucophane in XP.	Pale Yellow / Purple / Blue / Pleochroic	Moderate. 0.02 up to Low 2^nd order	Moderate	May be zoned / Length Slow	Good. 2 sets at 124°	Inclined 5°	Prisms / Fibrous	Small to Moderate 0-50°	Negative	Metamorphic (High P Low T)	Albite Biotite Hornblende K-Feldspar Microcline Plagioclase Sphene Volcanic Glass	Alkali Amphibole	Monoclinic
Goethite	Yellow / Orange Brown / Pleochroic	Very High	Very High	Component of Limonite	Good	Straight	Needles / Radial Fibrous / Oolitic spheres	Small	Negative	Igneous / Metamorphic (in weathered and altered Fe-minerals and rocks, Cavity and Fracture Filling, Fe-ore deposits)	Aegirine-Augite K-Feldspar Anorthoclase Nepheline Riebeckite Sodalite	Oxide	Orthorhombic
Graphite	Greenish Gray / Opaque		Very Low to Very High	Smeared margins / Often in Barrovian foliated rocks (e.g. Phyllite or Gneisses)	Perfect		Flakes / Grains			Metamorphic	Biotite Cordierite Corundum Kyanite Quartz Spinel		Hexagonal
Grossularite	Colourless / Green to Yellow	Isotropic (may be anomalous)	High	Zonal growth rings / Mottled colour texture	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Metamorphic (e.g. Marbles) / Sedimentary (e.g. Limestones)	Biotite Clinopyroxenes Hornblende Orthopyroxenes Plagioclase Quartz	Garnet	Cubic
Grünerite	Colourless to Pale Brown	Moderate to High. 0.02-0.045	Moderate to High	Lamellar Twinning	Good. 2 sets at 124° (Amphibole Cleavage)	Inclined 10-20°	Prisms	Moderate to Large 60-85°	Positive or Negative	Metamorphic / rare in igneous		Amphibole	Monoclinic
Gypsum Gypsum in PPL.	Colourless	Very Low	Very Low to Low	Tends to be distorted / Polysynthetic twinning can form during thin-section making / Simple Twinning	Good. 3 sets	Inclined 15°	Plates / Fibrous / Granular	Moderate to Small 58°	Positive	Sedimentary			Monoclinic
Harmotome	Colourless	Very Low	Very Low	Heating during thin-section making changes the optical characteristics		Inclined 28-32°	Thick Columns / Elongate Prisms	Large to Small 79°	Positive	Igneous (Cavity and Fractures Filling in basic Volcanic rocks, in veins in plutonic rocks)		Cubic Zeolite	Monoclinic
Hastingsite Group	Bright Green to Yellow Green / Pleochroic	Very Low	Moderate to High	May have pleochroic haloes / Use associated minerals to distinguish from other amphiboles / Alters to Actinolite, Antigorite, Chlorite / Length Slow		Inclined 14-20°	Short to Long Columns / Needles / Elongate Prisms	Moderate to Large 34-90°	Negative	Igneous (Intermediate to acidic rocks and Lamprophyrs) / Metamorphic (Amphibolite and Amphibole Schists)	Andalusite Biotite Cordierite K-Feldspar Kyanite Muscovite Plagioclase Quartz	Green Hornblende Amphibole	Monoclinic
Haüyne Haüyne in PPL. Haüyne in XP.	Colourless / Blue / Purple Blue / Blue Green	Isotropic	Moderate Negative	Dark rims, opaque streaks and clusters / Zoned / Irregular colour distribution / Locally as fine-grained inclusions	Good	Isotropic	Hexagonal / Cubes / Anhedral / Corroded crystals /	Isotropic	Isotropic	Igneous (Mainly alkaline volcanic, rarely plutonic)	Leucite Nepheline	Sodalite (Feldspathoid)	Cubic
Hematite Hematite in PPL.	Blood Red / Opaque	Not detectable	Very High	Normally Opaque / Grains may be deep Red on thin edges / Mainly in schists or as accessory mineral in other rocks.	None	Straight	Hexagonal Plates / Granular / Tabular / Fibrous	Uniaxial (Opaque)	Negative	Igneous / Metamorphic (Low to Medium grade) / Sedimentary	Clinopyroxenes Leucite Melanite Nepheline Olivine Titanaugite Volcanic Glass / Never With Quartz	Oxide	Trigonal
Hercynite Hercynite in PPL. Hercynite in XP.	Deep, "Emerald" Green	Isotropic	High	May be zoned with a darker core / Simple Twinning		Isotropic	Octahedral / Granular	Isotropic	Isotropic	Igneous (Ultramafic rocks) / Metamorphic (Cordierite Sillimanite Gneisses)	Aegirine-Augite Apatite Nepheline K-Feldspar Plagioclase Quartz Sanidine	Spinel	Cubic
Heulandite	Colourless	Very Low	Very Low	Simple Twinning / May occur as Devitrification Product / Length Fast	Perfect	Inclined 0-32°	Platy / Flaky / Radiating / Rosettes / Subparallel Aggregates	Small to Moderate 0-50°	Positive	Igneous (Cavity and Fractures Filling in acidic to basic magmatic rocks) / Metamorphic (in metatuffs and metagreywackes in Zeolite facies)	Almandine Cordierite Corundum	Flaky Zeolite	Monoclinic
Hornblende Hornblende in PPL. Hornblende in XP.	Green / Brown / Red / orange / Pleochroic	Low to Moderate. 0.015-0.02 up to mid 2^nd order	High	Colour of metamorphic Hornblendes often related to grade: Low to high grade goes from Bluish Green to Green to Brownish / Occurs in intermediate Igneous rocks / Occurs in medium grade metamorphic rocks	Good. 2 sets at 120°	Inclined 2-4°	Elongate Prisms / Laths	Moderate to Large 50-80°	Negative	Igneous / Metamorphic (Med grade)	Albite Almandine Biotite Kyanite Muscovite Quartz	Amphibole	Monoclinic
Hypersthene	Pale Green / Reddish / Pale Brown / Weakly Pleochroic	Very High	Moderate to High	Outdated term for a mineral in the Enstatite-Ferrosilite series / Zoning with Mg-rich core in Colcanic rocks / often with exsolution lamellae in Plutonic rocks / Alters to serpentine	Good. 2 sets		Short Columns / Granular / Elongate Prisms	Moderate 63-45°	Negative	Igneous (Intermediate to acidic Volcanic rocks) / Metamorphic (Contact metamorphism, Pyroxene Granulites)	Calcite Glaucophane Chlorite Garnet Quartz Sericite Sphene	Orthopyroxene	Orthorhombic
Illite	Colourless	High. 0.030-0.035	Low	Coats grain surface / Extremely fine	Perfect	-	Fibrous / Wispy / Very fine	Small 5-25°	Negative	Sedimentary	Antigorite Actinolite Clinochore Quartz Tremolite	Mica	Monoclinic
Ilmenite Ilmenite in PPL. Ilmenite in XP.	Red in thin flakes or Opaque	Not detectable	Very High	Common accessory mineral	None	Straight	Hexagonal Plates / Laminar / Prismatic / Skeletal / Granular / Flaky	Uniaxial (Opaque)	Negative	Igneous / Metamorphic (High grade) / Sedimentary	Apatite Beryl Cassiterite Fluorite Spodumene Topaz	Oxide	Trigonal
Jadeite Jadeite in PPL. Jadeite in XP.	Colourless to Pale Green / Weakly Pleochroic	Low. 0.006 anomalous	Moderate	Occurs in Glaucophane rocks and Jadeite-Quartzites	Good. 2 sets at 87°	Inclined 30-50° / May be Undulose	Prisms / Hexagonal / Needles	Large 60-90°	Positive	Metamorphic	Albite Epidote Biotite Sphene Talc Calcite Chlorite Quartz Sericite	Clinopyroxene	Monoclinic
Kaersutite Kaersutite in PPL. Kaersutite in XP.	Reddish Brown / Pleochroic	Very High	Moderate to High	May have zoned colour distribution / Hourglass structure / Reaction Rims / Length Slow		Inclined 3-19°	Short Columns / Elongate Prisms	Large 74-82°	Negative	Igneous (Na-rich basic rocks)	Cristobalite	Brown Hornblende Amphibole	Monoclinic
Kaolinite	Colourless / Pale Yellow	Low. 0.007	Low	Stacks of tiny plates / Often fills pore space / from the alteration of Feldspars	Perfect	-	Plates / Fibrous / Radiating platelets	Small to Moderate 25-50°	Negative	Sedimentary	Calcite Diopside Epidote Grossularite Quartz Vesuvianite	Clay / Sheet	Triclinic / Monoclinic
Katophorite	Greenish Brown	Very Low	Moderate to High	May have zoned colour distribution / Hourglass structure / Reaction Rims / Length Slow		Inclined 8-16°		Small to Moderate 0-57°	Negative	Igneous (Na-rich Magmatites)		Brown Hornblende Amphibole	Monoclinic
Koppite	Colourless / Red to Brown	Isotropic	Very High	Simple Twinning / Hard to differentiate from Perovskite, Picotite, Cromite and Melanite		Isotropic	Euhedral (Dodecahedrons; like a Hexagon with more faces)	Isotropic	Isotropic	Igneous (Carbonatites)	Apatite Biotite Hornblende Or Nepheline K-Feldspar Quartz		Cubic
Kyanite Kyanite in PPL. Kyanite in XP.	Colourless / Pale Blue Pleochroic	Low. 0.012-0.016 up to 1^st order Yellow	High > Andalusite and Sillimanite	Stress induced curving / Length Slow	Perfect. 2 sets at 85°	Inclined 0-30°max	Prisms	Large 85°	Negative	Metamorphic (Moderate to high grade metapelites)	Actinolite Albite Chlorite Clinozoisite Epidote Prehnite Sericite	Al Silicate	Triclinic
Labradorite	Colourless	Low. up to White	Low	Albite Twinning lengthways / Carlsbad Twinning / Often zoned: typically Anorthite (Na-rich) centres and Albite (Ca-rich) rims. Anorthite cores tend to alter to a fine-grained, turbid, white mica (Sericite) / Often with Clinopyroxene and/or Olivine in Igenous rocks.	Perfect and Good. 2 sets at 86°	Inclined 28-39°	Prisms / Rectangular Laths	Large 70-90°	Negative	Igenous / Metamorphic (High grade)	Fluorite K-Feldspar Li-Mica Quartz Rutile Topaz Tourmaline	Plagioclase Feldspar	Triclinic
Laumontite	Colourless	Very Low	Very Low	Extinction angle related to degree of water loss / Length Slow		Inclined 8-11°	Radial / Columns / Elongate Prisms / Spherulitic	Moderate 33-47°	Negative	Igneous (Cavity and Fractures Filling in acidic to basic magmatic rocks) / Metamorphic (in metatuffs and metagreywackes in Zeolite facies)	Zircon Cassiterite Ilmenite Rutile	Mordenite Fibrous Zeolite	Monoclinic
Lawsonite Lawsonite in PPL. Lawsonite in XP.	Colourless / Rare Blueish	Moderate. 0.020	Moderate	Lamellar Twinning / Length Fast / in Glaucophane schists, Greenschist and amphibolites	Perfect. 2 sets	Straight / May be Undulose	Diamond / Prisms / Plates	Large 76-87°	Positive	Metamorphic	Leucite Nepheline Olivine Perovskite Pyroxene Never With Quartz	Epidote	Orthorhombic
Lepidolite	Colourless / Pale pink / Weakly Pleochroic	Very High	Very Low to Moderate	Pleochroic haloes around zircon / Occurs as fine-speckled in extinction orientation / Length Slow	Perfect	Straight (Parallel to Cleavage)	Platy / Flaky / Scaly / Columns	Small to Moderate 23-58°	Negative	Igneous (Li-rich Granite Pegmatites) / Metamorphic (Greisen)	Leucite Nepheline Olivine Perovskite Pyroxene Never With Quartz	Lithionite Series Mica	Monoclinic
Leucite Leucite in PPL. Leucite in XP.	Colourless	Very Low. Almost Isotropic. 0.001 / Anomalous	Moderate Negative	Multiple Twinning / Volcanic only	Poor	Straight	Euhedral (Icositetrahedral) / Trapeze shaped	Almost Isotropic	Positive	Igneous	Opal Zeolites	Feldspathoid	Tetragonal / Pseudo Cubic
Limonite	Ochre-Yellow to Reddish-Brown	Very Low / Opaque if dendritic	Very High to Very Low	Broad term for unidentifiable massive Fe oxides / No visible crystals / Most commonly just Goethite	None		Oolitic spheres / Crust and Soil-Like / Radiating			From alteration of Hematite or Magnetite / Igneous / Metamorphic / Sedimentary	Cristobalite Tridymite Volcanic Glass	Oxide	-
Lizardite	Colourless to Pale Green / Weakly Pleochroic	Very Low	Low	Main phase in Bastite (Pseudomorphous after orthopyroxenes) / Length Slow	Perfect	Straight	Fine-Scaly / Fibrous	Small 0°	Negative	Metamorphic (Serpentinites)	Analcite Calcite Zeolites	Serpentine	Monoclinic
Magnesite Magnesite in PPL. Magnesite in XP.	Colourless / Gray Brown	Very High	Very Low to High	May have Lamellar Twinning / Length Fast		Straight	Granular / Fibrous / Dense	Uniaxial	Negative	Metamorphic (Talc and chlorite schist, as gel in serpentinites, as ore deposit in metasomatic zones)		Carbonate	Trigonal
Magnetite Magnetite in PPL. Magnetite in XP.	Opaque	Isotropic if translucent	Very High	Magnetic / AKA Lodestone	None	Isotropic	Cubes / Octahedral / Granular / Skeletal	Isotropic	Isotropic	Igneous / Metamorphic / Sedimentary		Oxide	Cubic
Melanite	Brown	Isotropic	Very High	Zonal texture	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Igneous (Alkaline rocks)		Garnet	Cubic
Mesolite	Colourless	Very Low	Very Low	Isotypic (Similar crystal structure and chemical formula) with Natrolite and Scolecite / Length Fast		Inclined 2-5°	Fibrous	Large to Small 80°	Positive	Igneous (Cavity filling in phonolites and basalts)		Natrolite Fibrous Zeolite	Monoclinic
Microcline Microcline in XP.	Colourless	Low. 0.006-0.010 up to Gray	Very Low	Cross-hatch Twinning	Perfect. 2 sets	Inclined	Prisms	Moderate to Large 60-80°	Negative	Igneous / Metamorphic (Med to High Grade) / Sedimentary	Calcite Epidote Fassaite Grossularite Sphene Spinel Wollastonite	Alkali Feldspar	Triclinic
Monazite	Colourless / Green - Yellow / Weakly pleochroic	High to Very High	High	Simple Twinning / May be fractured / May look like Zircon or Sphene / Higher birefringence and less pleochroic than Staurolite	Good	Straight / May be Inclined 2-6°	Tabular / Plates	Small 10-25°	Positive	Igneous (Granites) / Metamorphic (Dolostones and Mica Schists) / Sedimentary (highly resistant to weathering)	Epidote Cordierite Apatite Ilmenite Bastnasite	Phosphate	Monoclinic
Mordenite	Colourless / Red	Very Low	Very Low	May occur as Devitrification Product	Good	Straight	Fibrous / Radial / Fine grained	Large 76-90°	Positive / Negative	Igneous (Cavity and Fractures Filling in acidic Volcanic rocks) / Sedimentary	Cassiterite Li-Mica Quartz Topaz Tourmaline	Mordenite Fibrous Zeolite	Orthorhombic
Muscovite Muscovite in XP.	Colourless / Pale Yellow / Pale Green (Cr-rich)	High. 0.036-0.04 up to upper 2^nd order	Moderate	Cleavage kink due to deformation / Length Slow	Perfect	Straight or 1-2° (Undulose)	Plates / Fine aggregates / Flakes	Moderate 30-50°	Negative	Igneous (Al-rich granites) / Metamorphic / Sedimentary	Calcite Zeolite	Mica	Monoclinic
Natrolite Natrolite in PPL. Natrolite in XP.	Colourless	Very Low	Very Low	Pseudomorphous after Plagioclases / Length Slow	Good	Straight	Radiating Needles / Lath / Fibrous / Radiating Aggregates	Moderate 58-64°	Positive	Igneous (Cavity filling in basic to intermediate magmatic rocks)	Clinopyroxenes Olivine Plagioclase Spinel	Natrolite Fibrous Zeolite	Orthorhombic
Nepheline Nepheline in PPL. Nepheline in XP.	Colourless / Cloudy from inclusions	Low. 0.009-0.005 (<quartz) up to dark Gray	Low Negative	Euhedral blocky shapes (i.e. hexagons or rectangles) are only seen in lavas, Anhedral elsewhere / Length Fast	Poor	Straight	Hexagonal / Prisms / Euhedral blocks	Uniaxial	Negative	Igneous (Alkali rocks)	Clinopyroxenes Olivine Plagioclase Spinel	Feldspathoid	Hexagonal
Nosean	Colourless	Isotropic	Moderate Negative	Dark rims, opaque streaks and clusters / Zoned / Irregular colour distribution / Locally as fine-grained inclusions	Poor	Isotropic	Hexagonal / Cubes / Anhedral corroded crystals /	Isotropic	Isotropic	Igneous (Mainly alkaline volcanic, rarely plutonic)	Biotite Clinopyroxenes Hornblende Plagioclase Volcanic Glass	Sodalite (Feldspathoid)	Cubic
Oligoclase	Colourless	Low. up to White	Very Low	Albite Twinning lengthways / Carlsbad Twinning / Often zoned: typically Anorthite (Na-rich) centres and Albite (Ca-rich) rims. Anorthite cores tend to alter to a fine-grained, turbid, white mica (Sericite) / Often with Biotite and K-feldspar in Igneous rocks / In low-med grade metamorphic rocks	Perfect and Good. 2 sets at 86°	Inclined 12°	Prisms / Rectangular Laths	Large 70-90°	Negative	Igenous / Metamorphic (Low grade)	Clinopyroxenes Leucite Nepheline Olivine Plagioclase Sodalites	Plagioclase Feldspar	Triclinic
Olivine Group Olivine in PPL. Olivine in XP.	Colourless (Mg-rich) to Yellow or Pale Brown (Fe-rich)	High. 0.032-0.05 up to upper 2^nd order, or 3^st in Fayalite (Fe-rich Olivines)	High	May have different birefringence colours along curving cracks / May alter to serpentine / Occurs in basic and ultrabasic igneous rocks / Occurs in meta marbles / Fayalite (Fe-rich olivines) rare in granitic and syenitic rocks.	None. Curving Cracks	Straight	Diamond / Hexagonal / Octahedral / Granular	Uniaxial	Positive for Forsterite (Mg-rich) / Negative for Fayalite (Fe-rich)	Igneous (Basic to Ultrabasic) / Metamorphic (e.g. Serpentinites, Marbles)	Biotite Garnet MicroclineK-Feldspar Plagioclase Pyroxene Quartz Sphene	Olivine	Orthorhombic
Omphacite Omphacite in PPL. Omphacite in XP.	Colourless to Pale Green / faintly Pleochroic	Low. 0.012 moderately anomalous	Moderate to High	Like Augite but with lower Birefringence	Good . 2 sets at 87°	Inclined 34-48°	Prisms / Hexagonal	Moderate to Large 55-85°	Positive	Metamorphic (Only Eclogites)	Biotite Garnet MicroclineK-Feldspar Plagioclase Pyroxene Quartz Sphene	Clinopyroxene	Monoclinic
Opal	Colourless / Yellowish / Reddish	Anomalous	Very Low	Often altered to Cristobalite or Chalcedony / Shrinkage cracks / Hydrated SiO₂	Not a crystal		Amorphous / Spherical	Not a crystal	Not a crystal	Igneous (Volcanic)	Albite Almandine Epidote	Oxide
Orthoclase / K-Feldspar	Colourless	Low. 0.006-0.010 up to Gray	Low	Carlsbad Twinning / Perthitic Exsolution common / Often turbid	Perfect. 2sets at 90°	Straight	Prisms	Large 60-80°	Negative	Igneous (Acid to Intermediate rocks, Volcanic) / Metamorphic (Orthogneiss)	Biotite Clinopyroxene Orthopyroxene Plagioclase Volcanic Glass	Alkali Feldspar	Monoclinic
Orthopyroxene Group Orthopyroxene in PPL. Orthopyroxene in XP.	Colourless to Pale Pink / Green Pleochroic	Low. 0.007 to Moderate at Ferrosilite (Fe-rich). up to 1^st order Yellow	Moderate to High	Pleochroic grains usually have a negative optic sign / Occurs in basic and ultrabasic rocks / Occurs in high-grade metamorphic rocks (i.e. metabasites) / Length Fast	Good. 2 sets at 87°	Straight	Prisms / Hexagonal	Moderate to Large 55-90°	Positive for 88-100 Fe% / Negative at 12-88 Fe%	Igneous / Metamorphic	Olivine Plagioclase Titanaugite	Pyroxene	Orthorhombic
Oxybiotite	Red to Dark Brown	Very Low	Moderate to High	Reaction Rims / Pleochroic haloes around Zircon / Occurs as fine-speckled in extinction orientation / Length Slow	Perfect	Straight (Parallel to Cleavage)	Platy / Flaky / Scaly / Columns	Small 20-30°	Negative	Igneous (Intermediate Volcanic rocks)	Aegirine-Augite Apatite Arfvedsonite Nepheline Sanidine Olivine Titanbiotite	Mica	Monoclinic
Oxyhornblende	Red to Dark Brown	Very Low	Moderate to High	Changeable relief and birefringence in a single crystal / Haloes / Reaction Rims / Length Slow	Perfect. 2 sets at 124°	Straight to Inclined 12°	Short to Long Columns	Moderate to Large 56-88°	Negative	Igneous (Acidic to intermediate Volcanic rocks)	Aegirine-Augite Anorthoclase K-Feldspar Nepheline Riebeckite Sodalite	Brown Hornblende Amphibole	Monoclinic
Paragonite	Colourless	High. 0.036-0.04	Moderate		Perfect	Straight or 1-2° (Undulose)	Plates	Moderate 40°	Negative	Metamorphic / Sedimentary	Beryl Cassiterite Quartz Spodumene Topaz Tourmaline	Mica	Monoclinic
Perovskite Perovskite in PPL.	Colourless / Dark Brown / Yellowish / Greenish	Isotropic / Very weak / Anomalous	Very High	May have zoned colour distribution / Very small grains are opaque / Simple and Lamellar Twinning	Poor	Almost Isotropic	Octahedral / Cubes	Almost Isotropic	Positive	Igneous (Kimberlites, Alkaline and Volcanic rocks)	Cassiterite Quartz Topaz Wolframite	Pervoskite	Orthorhombic
Phengite	Colourless / Pale Green	High. 0.036-0.04	Moderate	A Si-rich Muscovite / Can't be distinguished from Muscovite Optically / Length Slow	Perfect	Straight or 1-2° (Undulose)	Fine aggregates / Flakes	Moderate 25-35°	Negative	Igneous / Metamorphic (Glaucophane schist, Eclogite, Gneiss)	Clino And Orthopyroxenes Oxyhornblende Plagioclase Quartz Volcanic Glass Sanidine	Mica	Monoclinic
Phillipsite Phillipsite in PPL. Phillipsite in XP.	Colourless	Very Low	Very Low	Interpenetrating Twinning / Occurs in basalt cavities / Length Slow		Inclined 11-30°	Thick Columns	Moderate to Large 60-80°	Positive	Igneous (Cavity and Fractures Filling in basic Volcanic rocks, Nepheline syenite)	Aegirine-Augite Apatite Na-Sanidine Nepheline Nosean	Cubic Zeolite	Monoclinic
Phlogopite Phlogopite in XP.	Colourless / Pale Yellow and Green / Orange / Pink / Brown	High. 0.028-0.045	Low to Moderate	A Mg-rich Mica / Pleochroic Haloes around inclusions / Length Slow	Perfect	Straight or slightly Inclined	Needles / Elongate Laths / Micaceous Flakes	Small <15°	Negative	Igneous (Basic and Ultrabasic, Kimberlites) / Metamorphic (Marbles)	Calcite Pyrite Quartz	Biotite Mica	Monoclinic
Picotite	Yellow to Brown	Isotropic	Very High to Very Low	Occurs as small inclusions in Olivines or Serpentine / Simple Twinning		Isotropic	Granular within Olivine or Serpentine	Isotropic	Isotropic	Igneous (Alkali basalts)	Calcite Chlorite Chrysotile Olivine Pyroxene Zeolite	Spinel	Cubic
Piemontite Piemontite in PPL. Piemontite in XP.	Yellow / Pink / Magenta / Deep Brown Pleochroism	Low to High. 0.025-0.075 / May be Anomalous	High	A Mn-rich Epidote	Good. 2 sets	Straight or Inclined	Prisms	Moderate to Large 50-85°	Positive	Metamorphic	Hornblende Microcline OlivineK-Feldspar Pyroxene Quartz Serpentine	Epidote	Monoclinic
Pigeonite	Colourless to Greenish Pinkish or Brownish	Moderate to High. 0.023-0.029	Moderate to High	May alter along cracks / Lamellar Twinning / Often as matrix	Good. 2 sets at 87°	Inclined 37-44°	Prisms / Hexagonal	Small 0-30°	Positive	Igneous (Ti-rich Alkali Rocks)	Amphibole Biotite Delessite Pyroxene	Clinopyroxene	Monoclinic
Plagioclase Group Plagioclase in XP.	Colourless	Very Low. 0.007-0.013	Low	Lamellar Twinning	Perfect	Inclined	Prisms	Large	Positive for Ab 77, Negative for An 78	Igneous / Metamorphic / Sedimentary	Actinolite Albite Biotite Epidote Glaucophane Lawsonite Pumpellyite Quartz Sericite Zoisite	Plagioclase Feldspar	Triclinic
Pleonaste	Greenish Gray	Isotropic	High to Very Low	Simple Twinning		Isotropic	Octahedral	Isotropic	Isotropic	Igneous (Mafic) / Metamorphic (e.g. Marbles)	Chrysotile Magnesite Olivine Orthopyroxene Talc	Spinel	Cubic
Prehnite Prehnite in PPL. Prehnite in XP.	Colourless	Very Low / May be Anomalous Blue to Brown	Moderate	Lamellar Twinning	Good	Straight	Plates / Flaky / Radiating Aggregates / Dendritic / Skeletal	Moderate to Large 64-71°	Positive	Igneous (Basic Volcanic rocks) / Metamorphic (Greenschists, metabasalts and in metamorphic siliceous limestones)		Alumino-Silicate	Orthorhombic
Pumpellyite Pumpellyite in PPL. Pumpellyite in XP.	Colourless / Green / Blue-Gray / Brownish / Pleochroic	Low to Moderate / May be anomalous Blue to Brown	Moderate to High	Twinning / Zoned / Intergrown with Lawsonite	Good. 2 sets	Inclined 5-22°	Radiating Rays / Laths / Needles / Fibrous / Rosettes	Small to Large 7-110°	Positive or Negative	Metamorphic (Green and Blueschist)	Antigorite Bronzite Chrysotile	Pumpellyite Epidote	Monoclinic
Pyrite Pyrite in PPL. Pyrite in XP.	Opaque	Isotropic	High	Hard to ID in Transmitted light / Often weathered / Interpenetrating Twinning		Isotropic	Octahedral / Cubes / Granular	Isotropic	Isotropic	Igneous / Metamorphic (Schists) / Sedimentary	Aegirine-Augite Aenigmatite Arfvedsonite Quartz Volcanic Glass		Cubic
Pyrochlore	Reddish to Opaque Brown	Isotropic	Very High	Simple Twinning / Hard to differentiate from Perovskite, Picotite, Chromite and Melanite		Isotropic	Octahedral / Granular	Isotropic	Isotropic	Igneous (Pegmatites and Volcanic ejections)	Analcite Calcite Heulandite Laumontite Na-Sanidine Nepheline Scolecite Stilbite Thomsonite		Cubic
Pyrope	Pale Red	Isotropic	Very Low	Celyphytic rims common	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Metamorphic (Peridotites, Kimberlites, Serpentinites and Eclogites)	Calcite Chalcedony Zeolite	Garnet	Cubic
Pyrrhotite	Opaque		Very Low	Hard to ID in Transmitted light			Granular / Tabular/ Massive			Igneous (Mafic to Ultramafic)	Albite Analcite Calcite Chabazite Chalcedony Chlorite Heulandite Natrolite Scolecite Stilbite Thomsonite		Hexagonal
Quartz Quartz in PPL. Quartz in XP.	Colourless	Low. 0.009 up to cream	Low	Length Slow	None	Straight if Prisms edge visible (may be Undulose)	Irregular Prisms	Uniaxial	Positive	Igneous / Metamorphic (Low grade) / Sedimentary	Albite Analcite Calcite Chabazite Chalcedony Chlorite Heulandite Natrolite Scolecite Stilbite Thomsonite	Framework SiO₂	Trigonal
Riebeckite	Green / Purple / Brown / Dark Blue / Pleochroic	Low. 0.006-0.016 / May be anomalous	Moderate to High	Length Fast	Good. 2 sets at 124°	Inclined 3-15°	Short Prisms / Needles	Moderate to Large 40-100°	Negative to Positive	Igneous (Na-rch) / Metamorphic	Heulandite Laumontite Stilbite	Alkali Amphibole	Monoclinic
Rutile Rutile in PPL. Rutile in XP.	Deep Reddish Brown / Yellow Brown / Opaque	Very High. 0.29	Very High	Occurs in coarse-grained, high pressure, metamorphic rocks (e.g. eclogites, or kyanite-bearing) / Occurs in Igneous rocks as tiny grains (may be opaque) / May have radioactive haloes / Length Slow	Good	Straight (Not easy to see)	Granules / Plates	Uniaxial	Positive	Metamorphic (High-P) / Igneous	Albite Apophyllite Calcite Chlorite Epidote Prehnite Quartz Zeolite	Oxide	Tetragonal
Sanidine Sanidine in PPL. Sanidine in XP.	Colourless	Low. 0.006-0.008	Low	Small 2V is key / Carlsbad Twinning	Perfect	Straight	Prisms	Small to Moderate 0-60°	Negative	Igneous	Analcite Laumontite Quartz Stilbite	Alkali Feldspar	Monoclinic
Sapphirine Sapphirine in PPL. Sapphirine in XP.	Colourless / Pale Blue Pleochroic	Very Low to Low. 0.005-0.009 anomalous	High	Often in Symplectite associations	Moderate	Straight or slightly Inclined	Irregular	Moderate to Large	Negative	Metamorphic	Calcite Clay Minerals Heulandite Laumontite Quartz	Pyroxene	Monoclinic
Scapolite Group Scapolite in PPL. Scapolite in XP.	Colourless / Yellow	Very Low (Na) to High (Ca)	Low to Moderate	May be cloudy / Fluid and mineral inclusions common / Scapolite group is a series between Marialite and Meionite	Good. 2 sets	Straight or symmetrical to cleavage	Cubes / Prisms	Uniaxial	Negative	Igneous / Metamorphic	Chabazite Heulandite Laumontite Mordenite Scolecite Stilbite	Framework	Tetragonal
Scolecite	Colourless	Very Low	Very Low	Simple Twinning / Length Fast	Good	Inclined 15-18°	Fibrous / Radial	Moderate 36-58°	Negative	Igneous (Amygdules in basic to ultramafic magmatic rocks) / Metamorphic (Fracture filling)	Analcite Calcite Chabazite Chalcedony Natrolite Thomsonite	Natrolite Fibrous Zeolite	Monoclinic
Sericite Sericite in PPL. Sericite in XP.	Colourless	Moderate to High	Low to Moderate	From the hydrothermal alteration of Orthoclase or Plagioclase / Variety of Muscovite	Good	Straight	Flakes / Irregular Granules	Moderate 30-50°	Negative	Metamorphic	Feldspars Biotite Muscovite Ore Deposits Tin Copper Quartz Pyrite Fluorite Epidote Calcite	Mica	Monoclinic
Serpentine Group Serpentine in PPL. Serpentine in XP.	Colourless	Low. 0.006-0.013	Low Positive	Mineral group with Lizardite, Chrysotile, Antigorite/ Mesh window texture / From the alteration of Olivine	Good	Straight	Fibrous / Flakes	Uniaxial or Moderate	Negative	Igneous / Metamorphic	Calcite Hyalophane Laumontite Natrolite	Sheet	Trigonal / Monoclinic / Orthorhombic
Siderite	Colourless to Pale Yellow Brown	Very High	Moderate to Very High	Carbonates with the highest relief and birefringence / Simple Twinning / Length Fast		Straight	Granular / Oolitic spheres / Needles / Dendritic Aggregates / Skeletal	Uniaxial	Negative	Metamorphic (as gangue in ore body, as ore in metasomatic and hydrothermal deposits)	Analcite Calcite Phillipsite Thomsonite	Carbonate	Trigonal
Sillimanite Sillimanite in PPL. Sillimanite in XP.	Colourless / Rare Brown	Moderate. 0.018-0.022 up to mid 2^nd order.	High	Higher briefringence and relief than Andalusite / Fibrous texture often associated with Biotite / Needles often associated with Quartz / Length Slow	Good	Straight	Fibrous (Fibrolite) or Diamond/ Needles	Small 20-30°	Positive	High T Metamorphic	Aegirine-Augite Anorthoclase Arfvedsonite Riebeckite	Al Silicate	Orthorhombic
Smectite Group	Colourless / Pale Brown / Yellow / Olive-Green	Moderate to High	Low	Group of Clay minerals / Fills pores / Main constituent of Bentonite	Perfect	-	Irregular Plates	-	Negative	Sedimentary	Beryl Cassiterite Wolframite Fluorite Li-Mica Quartz Tourmaline	Clay / Sheet	Monoclinic
Sodalite Sodalite in PPL. Sodalite in XP.	Colourless / Pale Gray	Isotropic	Moderate Negative	Simple Twinning / Slight birefringence around inclusions	Poor	Isotropic	Anhedral to Euhedral / Cubes / Hexagonal / Corroded-looking	Isotropic	Isotropic	Igneous (Mainly alkaline volcanic)	Calcite Gypsum Halite Quartz	Sodalite (Feldspathoid)	Cubic
Spessartine	Pale Yellow	Isotropic	High	with Almandine	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Metamorphic (Hornfels) / Sedimentary	Anhydrite Calcite Halite Quartz	Garnet	Cubic
Sphene / Titanite Sphene in PPL. Sphene in XP.	Colourless to Pale Brown	Very High. 0.1-0.2 Extreme - pinky buff colours	Very High	Occurs in intermediate and acid igneous rocks / Occurs in metabasites / Low birefringence grains seldom go fully extinct, going from dull anomalous orange to dull blue	Good	Inclined 35-50°	Commonly Diamond / Lozenge shaped	Small to Moderate 17-55°	Positive	Igneous (Intermediate and Acidic, never in Gabbro or Basalts) / Metamorphic (Amphibolites, Marbles)	Celestite Quartz	Humite	Monoclinic
Spinel Group	Colourless / Brown / Green / Pink / Pale Blue / Never Pleochroic	Isotropic if translucent	Very High	Simple Twinning / Transparent Spinels mainly in metamorphic rocks / Colourless Spinels in marbles / Coloured Spinels in high-grade metapelites / Deep Brown, Cr-rich, Spinels in basic and ultrabasic rocks	None	Isotropic	Cubes / Octahedral	Isotropic	Isotropic	Metamorphic	Hematite Lepidocrocite	Oxide / Spinel	Cubic
Staurolite Staurolite in PPL. Staurolite in XP.	Honey Yellow / Pleochroic	Low. 0.011-0.014 up to 1^st order Yellow	High	Only found in metapelites / Usually as porphyroblasts with quartz inclusions / Length Slow	Moderate	Straight	Short Prisms / Tabular	Large 80-90°	Positive	Metamorphic (Metapelites)	Kyanite Garnet Mica Biotite Sillimanite	Staurolite	Monoclinic / Orthorhombic
Stilbite	Colourless	Very Low	Very Low	Interpenetrating Twinning		Inclined 3-12°	Radial / Fibrous / Bundled Aggregates / Skeletal / Plates	Small to Moderate 30-49°	Negative	Igneous (Cavity and Fractures Filling in basic to acidic Volcanic rocks)	Clinopyroxenes Arfvedsonite K-Feldspar Nepheline Riebeckite	Flaky Zeolite	Monoclinic
Stilpnomelane Stilpnomelane in PPL. Stilpnomelane in XP.	Yellow / Green / Brown / Strongly Pleochroic	High to Very High. 0.03-0.11	Moderate to High	Cleavage less perfect than Biotite / Length Slow	Good	Straight	Elongate Prisms / Laths / Needles / Radiating / Flaky	Pseudo Uniaxial	Negative	Metamorphic (Phyllite, Schist, Quartzite, Blueschist)	Biotite Chlorite Hornblende Muscovite Quartz	Sheet	Triclinic / Monoclinic
Talc Talc in PPL. Talc in XP.	Colourless to Pale Green	High. 0.037-0.050	Moderate	Indisguishable from Sericite by microscope / Very soft clay / From the alteration of Mg Silicates / Length Slow	Perfect	Straight	Fibrous / Scaly	Small 0-30°	Negative	Metamorphic / Sedimentary		Clay / Sheet	Monoclinic
Thomsonite	Colourless	Very Low	Very Low to Low	Highest birefringence of all the Zeolites / May have Simple Twinning / Renamed in 1820 in honour of Scotsman Thomas Thomson, professor of chemistry at the University of Glasgow.	Perfect	Straight	Radially / Fibrous / Columns / Elongate Prism / Flaky	Moderate to Large 44-75°	Positive	Igneous (Amygdules in basic to ultramafic magmatic rocks) / Metamorphic (Fracture filling)	Calcite Clay Minerals Quartz	Natrolite Fibrous Zeolite	Orthorhombic
Titanaugite	Brown / Purple / Brownish Yellow / Pleochroic	Very High	High	Hourglass texture / Zoned / Anomalous Brown to Blue-Gray at extinction/ Twinning	Good. 2 sets at 87°	Inclined 32-55°	Short to Long Columns / Platy	Moderate 42-65°	Positive	Igneous (Ti-rich alkali rocks)	Alkali-Feldspar Volcanic Glass Tridymite Zeolite	Clinopyroxene	Monoclinic
Titanbiotite	Orange / Red Brown	Very Low	Moderate to High	Weathered grains are bleached / Pleochroic haloes around Zircon / Occurs as fine-speckled in extinction orientation / Length Slow	Perfect	Straight (Parallel to Cleavage)	Platy / Flaky / Scaly / Columns	Small to Moderate 5-38°	Negative	Igneous (Na-rich, Ti-rich magmatic rocks)	Chlorite K-Feldspar Mica Plagioclase Quartz Rutile	Mica	Monoclinic
Topaz Topaz in PPL. Topaz in XP.	Colourless	Very High	Moderate	Contains fluid inclusions / Length Slow / Named after Topasos Island in the Red Sea	Perfect	Straight	Short Columns / Needles / Laths / Granular	Moderate 48-68°	Positive	Metamorphic (Greisen and granitic contact metamorphism) / Igneous (Tin pegmatites)	Apatite Calcite Diopside Vesuvianite Wollastonite Quartz Mica Feldspar Fluorite Cassiterite Tourmaline		Orthorhombic
Tourmaline Tourmaline in PPL. Tourmaline in XP.	Opaque / Blue / Green / Yellow / Brown / Strongly Pleochroic	Moderate. 0.02-0.03 up to up 2^nd order.	Moderate	Pleochroism darkest when N-S / Often colour zoned / Radioactive haloes around Zircon / Good indication that the rock is Boron rich / Distinguished from biotite and hornblende by the lack of cleavage / Length Fast	Poor	Straight	Triangular / Prisms / Needle-like	Uniaxial	Negative	Igneous / Metamorphic	Topaz	Epidote	Trigonal
Tremolite Tremolite in PPL. Tremolite in XP.	Colourless to Green Pleochroic	Moderate. 0.027 up to mid 2^nd	Moderate	Colour more intense for Fe-rich Tremolites / Only found in carbonate-rich metamorphic rocks (e.g. marbles) / May have pleochroic haloes / Length Slow	Good. 2 sets at 124°	Inclined 30° max typically 10-15°	Fine Prisms / Laths / Fibrous / Needle-like	Large 80-90°	Negative	Metamorphic (Green and Blueschist, Serpentinite, Marbles)	Apatite Calcite Phlogopite	Actinolite Amphibole	Monoclinic
Tridymite	Colourless	Very Low. 0.002-0.004	Moderate Negative	Lines vesicles in high temperature lavas / High temperature polymorph of Quartz / Occurs in volcanic rocks / Fracture Filling / Twinning / Length Fast	Poor	Straight	Radiating Rays / Platy	Moderate to Large 40-90°	Positive	Igneous (Volcanic) Metamorphic (Sanidine facies contact met.)		Framework SiO₂	Orthorhombic
Tschermakite Group	Bright Green to Yellow Green / Pleochroic	Very High	Moderate to High	May have pleochroic haloes / Use associated minerals to distinguish from other amphiboles / Alters to Actinolite, Antigorite, Chlorite / Length Slow		Inclined 15-22°	Short to Long Columns / Needles	Moderate to Large 65-90°	Negative	Igneous (Intermediate to acidic rocks and Lamprophyrs) / Metamorphic (Amphibolite and Amphibole Schists)	Clinopyroxenes Leucite Nepheline Sanidine Sodalites	Green Hornblende Amphibole	Monoclinic
Uvarovite	Pale "Emerald" Green	Isotropic (may be anomalous)	Very High	Zonal growth rings / Mottled colour texture	None	Isotropic	Euhedral (Rhombic Dodecahedrons; like a Hexagon with more faces) / Anhedral Grains	Isotropic	Isotropic	Found in Chromite rich rocks	Tridymite Zeolite	Garnet	Cubic
Vesuvianite / Idocrase Vesuvianite in PPL. Vesuvianite in XP.	Colourless / Yellow / Green / Brown / Weakly Pleochroic	Low / May be anomalous Purple Blue or Leather Brown	High	May have zoned colour distribution / Hourglass texture	Poor	Straight	Short Prisms / Granular / Needles / Spherulitic	Uniaxial	Positive / Negative	Metamorphic (Contact metamorphism and marbles)	Olivine Serpentine		Tetragonal
Volcanic Glass	Colourless / Yellow to Brown	Opaque / Anomalous	Very Low to Moderate	Fluid textures / Contraction and Conchoidal fractures / Radial devitrification textures			Amorphous			Igneous (Volcanic rocks, dykes and sills)	Carbonates Serpentine	-	-
Wollastonite Wollastonite in PPL. Wollastonite in XP.	Colourless	Low. 0.013	Moderate	Refractive index < Diopside / Twinning / Poikiloblastic	Good. 3 sets at 84 and 70°	Inclined 30-40°	Prisms / Hexagonal / Needles	Moderate 35-60°	Negative	Metamorphic (Marbles)		Technically not a Pyroxene	Triclinic
Xenotime Xenotime in PPL. Xenotime in XP.	Colourless / Yellow / Green / Red / Weakly Pleochroic	Very High	High	May have Pleochroic haloes / Length Slow	Good	Straight	Short Prisms / Granular	Uniaxial	Positive	Igneous (Felsic rocks) / Metamorphic (Orthogneiss) / Sedimentary (Sandstones)		Phosphate	Tetragonal
Zeolite Group	Colourless	Low (1^st order White)	Low to Moderate Negative	Cavity filling in volcanic rocks	-	-	-	Uniaxial or Biaxial	Positive or Negative	Igneous	Olivine Phlogopite Pyroxene Serpentine	Feldspathoid	-
Zinnwaldite Zinnwaldite in PPL. Zinnwaldite in XP.	Colourless to Brown-grey / Weakly Blue Gray Pleochroic	Very High	Low to Moderate	Occurs as fine-speckled in extinction orientation / Length Slow	Perfect	Straight (Parallel to Cleavage)	Fan Shaped / Radiating / Platy / Flaky / Scaly / Columns	Small to Moderate 15-32°	Negative	Igneous (Granite Pegmatites) / Metamorphic (Greisen)	Cassiterite Clino And Ortho Pyroxene Ilmenite Magnetite Olivine Plagioclase	Lithionite Series Mica	Monoclinic
Zircon Zircon in PPL. Zircon in XP.	Colourless to Pale Brown / Greenish or Pink / Weak or No Pleochroism	High. 0.04-0.065 up to 3^rd order	Very High	Often within biotite / May have pleochroic haloes / May be zoned / Rich in inclusions / Occurs as rare detrital grains in Quartzites and mature sedimentary rocks / Length Slow	Poor	Straight	Prisms / Cubes / Small Euhedral crystals	Uniaxial	Positive	Igneous (often in nepheline syenites) / Metamorphic / Sedimentary		Humite	Tetragonal
Zoisite / Thulite	Colourless / Purple / Strongly Pleochroic	Very Low / Anomalous Blue to Brown	Moderate	Length Fast	Good. 2 sets	Straight	Prisms	Uniaxial	Positive	Metamorphic (Low Grade)		Epidote	Orthorhombic

Select below the properties that you can see under the microscope. The table will then display all the minerals that match that specific combination of properties.