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Identify polished ore minerals under reflected light

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.

Properties in bold are particularly distinct for that mineral. Click on the mineral name to see pictures.

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Mineral properties
Mineral Formula Colour Comparative Colour Bireflectance Anisotropy Relative Hardness Habit Noteworthy Features Associated Minerals Internal Reflections Reflectivity Hardness Crystal System Notes
Alabandite MnS Gray C to Sphalerite: distinctly lighter None Isotropic / sometimes weakly anomalous ~Sphalerite Euhedral crystals / Anhedral aggregates / similar to Sphalerite Cleavage / Lamellar Twinning / Zonal Textures Chalcopyrite Mn-Carbonate Mn-Sphalerite Pyrite Pyrolusite Pyrrhotite Common / dark Green to Brown Low 22% Soft (240-251) Cubic
Allargentum Ag1-xSbx White / slightly Grayish C to Silver: Grayish None Weak >Silver Lamellar intergrowths in Silver Silver None High 70% Hexagonal Originally identified as Dyscrasite (Ag3Sb)
Allemontite / Stibarsen A mixture of As or Sb with AsSb White Weak Distinct ~Antimony Very fine myrmekitic intergrowth best seen under high magnification Intergrowth is often more visible after slight oxidation or etching Stibnite in Co-Ni-Ag-Bi-As ores and pegmatites None Moderate to High 50-70% Extra Soft (85-100) Trigonal
Ancanthite Ag2S Gray with Greenish tint C to Galena, Silver: darker, Greenish Gray Very Weak Distinct if well polished Less than most minerals Euhedral Cubic crystals / Anhedral polycrystalline aggregates Twinning visible when well polished / Irregular inclusions in Galena Covellite Galena Polybasite Proustite Pyrargyrite Pyrite Sphalerite Tetrahedrite None Low 30% Extra Soft (23-26) Monoclinic (Pseudo-Cubic) Polishing scratches visible due of softness / The hi-T polymorph (Argentite) always returns to Acanthite on cooling. Evidence of Argentite is from the pseudomorphous Acanthite with its cubic morphology
Antimony Sb White C to Arsenic: slightly more White / C to Galena: brighter White / C to Silver: less bright / C to Dyscrasite: similar Weak Distinct / Yellowish Gray, Brownish, Blueish Gray >Stibnite <Arsenic Fine to coarse grain aggregates / rarely Euhedral Cleavage / Twinning (often polysynthetic) Arsenopyrite Co-Ni-Arsenides Pyrite Stibarsen Stibnite None High 73-78% Extra Soft (50-69) Trigonal
Argentite Ag2S Gray with Greenish tint C to Galena, Silver: darker, Greenish Gray Very Weak Distinct if well polished Less than most minerals Euhedral Cubic crystals / Anhedral polycrystalline aggregates Twinning visible when well polished / Irregular inclusions in Galena Covellite Galena Polybasite Proustite Pyrargyrite Pyrite Sphalerite Tetrahedrite None Low 30% Extra Soft (23-26) Monoclinic (Pseudo-Cubic) Polishing scratches visible due of softness / The hi-T polymorph (Argentite) always returns to Acanthite on cooling. Evidence of Argentite is from the pseudomorphous Acanthite with its cubic morphology
Arsenic As White / tarnishes rapidly C to Antimony: slightly darker Gray / C to Skutterudite and Safflorite: slightly darker Gray / C to Galena: White with a Creamy tint Grayish White to Yellow or Blueish Gray / Weak in air / distinct in oil Distinct / Gray to Yellowish Gray >Bismuth >Silver Fine to coarse grained Anhedral aggregates / Colloform bands Twinning / basal cleavage often visible Arsenopyrite Proustite Pyrite Rammelsbergite Skutterudite Stibarsen None High 51-56% Extra Soft to Soft (72-173) Trigonal Very fast (a few hours) tarnishing is typical
Arsenopyrite
n
Arsenopyrite in PPL. 
Arsenopyrite in XP. 
FeAsS White C to Pyrite: White / C to Loellingite, Safflorite: Creamy White / C to Antimony: Grayish White / C to Galena, Sphalerite: White with pale Yellow tint Weak Strong / Blue, Green >Skutterudite >Magnetite <Pyrite <Cobaltite Euhedral to Subhedral rhomb shapes / Anhedral Granular masses when abundant Lamellar Twinning common Chalcopyrite Cobaltite Galena Glaucodcot Gold Loellingite Molybdenite Pyrite Pyrrhotite Sphalerite None High 52% Hard to Very Hard (715-1354) Monoclinic
Berthierite FeSb2S4 White-Gray with Pink or Brown tint Strong and characteristic (//a) Brownish Pink (//b) Grayish White (//c) White Very Strong / Blue, Gray, White, Brown, Pink ~Stibnite <Sphalerite Euhedral Needlelike / Subhedral aggregates Arsenopyrite Chalcopyrite Galena Gudmundite Pyrite Pyrrhotite Sphalerite Stibnite None Low to Moderate 30-42% Soft (168-228) Orthorhombic
Bismuth Bi White to Creamy White / Pinkish Cream C to Silver: Creamy / C to Arsenic: Pinkish Creamy / C to Sulfosalts: Pinkish Creamy Weak but distinct Creamy to Pinkish Distinct to Strong <All associated minerals Irregular masses / with inclusions of Anhedral crystals Twinning common, can be induced by grinding or scratching Arsenopyrite Bismuthinite Cassiterite Chalcopyrite Co-Ni-Arsenides Galena Molybdenite Pyrite Pyrrhotite Silver Sphalerite Sulfosalts Wolframite None Moderate 42% Extra Soft (16-18) Trigonal
Bismuthinite
n
Bismuthinite in PPL. 
Bismuthinite in XP. Note the anisotropy. 
Bismuthinite in XP. Note the anisotropy. 
Bi2S3 White / in Oil with Blueish Gray tint C to Bismuth: darker, Blueish Gray / C to Chalcopyrite: Blueish Gray / C to Galena: lighter, Creamy White Weak to distinct (//a) Blueish Gray-White (//b) Gray-White (//c) Creamy White Very Strong / especially in oil / Gray, Yellow, Violet / Straight Extinction / Large crystals often undulose >Bismuth <Chalcopyrite Subhedral Lath-like / less commonly as Granular masses Cleavage / Stress-induced Twinning / Undulose Extinction often seen Arsenopyrite Bismuth Cassiterite Chalcopyrite Molybdenite Pyrite Pyrrhotite Sphalerite Stannite Wolframite None High 60-70% Soft (110-136) Orthorhombic
Bixbyite (Mn,Fe)2O3 Gray with Cream to Yellow tint C to Braunite, Jacobsite, Hausmannite: lighter, Yellowish / C to Hematite: Brownish Usually None / Sometimes very Weak in oil Isotropic / sometimes weakly anomalous >Hausmannite ~Braunite Euhedral crystals / Granular aggregates Cleavage / Lamellar Twinning / Zonal growth Braunite Hausmannite Hematite Pyrolusite None Moderate 37-49% Hard to Very Hard (946-1402) Cubic
Bornite
n
Bornite in PPL. 
Bornite in XP. 
Cu5FeS4 Pinkish Brown to Orange / tarnishes Purplish / Violet / Iridescent Weak bireflectance may be visible on grain boundaries Very weak >Galena >Chalcocite <Chalcopyrite Irregular polycrystalline aggregates / Coatings on Chalcopyrite / Lamellar intergrowth with Chalcopyrite Cleavage may be visible / Twinning rare and difficult to see / Lamellar exsolution / Replacement textures with Chalcopyrite Enargite Digenite common / Alters on grain boundaries and fractures to Covellite Chalcopyrite Covellite Digenite Enargite Galena Hematite Linnaeite Magnetite Pyrite Sphalerite Tetrahedrite None Low 2-22% Extra Soft (87-100) Orthorhombic (Pseudo-Tetragonal)
Boulangerite
n
Boulangerite in PPL. 
Boulangerite in XP. 
Boulangeritein XP. 
Pb5Sb4S11 White with Blueish Gray C to Galena: darker Greenish Gray / C to Stibnite: slightly lighter / C to Jamesonite: darker Distinct / Gray-White to Green-Gray Distinct / Tan, Brown, Blueish Gray <Galena Granular / Fibrous aggregates Chalcopyrite Galena Pb-Sb-Sulfosalts Sphalerite Tetrahedrite Rare / Red Low 22% Extra Soft to Soft (92-125) Monoclinic
Brannerite (U,Ca,Ce)(Ti,Fe)2O6 Gray None None Euhedral prisms / Needle-like grains / Subhedral aggregates Often forms as replacement (sometimes pseudomorph) after Uraninite and Rutile / May have "dusting" of small radiogenetic Galena crystals Anatase Coffinite Galena Magnetite Pitchblende Pyrite Pyrrhotite Rutile Sphalerite Tetrahedrite Uraninite Common / Coarse crystals: Brownish Gray / Fine grained material: Blue-Gray to Blueish White, dark Brown to Yellowish Moderate 37-42% Moderate (690) Monoclinic (Metamict)
Braunite (Mn,Fe,Si)2O3 Gray with Brownish tint C to Magnetite: less Brown / C to Pyrolusite, Psilomelane: darker / C to Manganite, Hausmanite: similar but weaker bireflectance / C to Bixbyite, Jacobsite: more Gray Weak but distinct / Gray Weak but distinct / Gray to Blue / often undulose >Magnetite <Bixbyite Anhedral Granular masses / Subhedral to Euhedral crystals Zonal Textures Bixbyite Hematite Jacobsite Magnetite Pyrolusite Rare / dark Brown to deep Red Low 15% Hard (920) Tetragonal
Bravoite (Fe,Ni,Co)S2 Composition dependent / Fe-rich: Creamy to Pinkish / Co- and Ni-rich: Pinkish to Brownish to Violet None None >Sphalerite <Pyrite Isolated cubes / Octahedral crystals Zonal texture very characteristic / Darker zones are Ni and Co rich Bismuth Chalcopyrite Galena Linnaeite Maucherite Niccolite Safflorite Siegenite Sphalerite Tetrahedrite None Low 18% Moderate to Very Hard (668-1535) Cubic
Breithauptite NiSb Pink with Violet tint C to Niccolite: darker, Violet tint Strong / Pinkish to Pinkish Violet Very Strong / Blueish Green, Blueish Gray, Violet Red <Niccolite >Rammelsbergite >Safflorite Subhedral to Euhedral grains Zonal Textures Ag-Sulfosalts Chromite Galena Niccolite Pentlandite Pyrrhotite Safflorite Silver None Moderate to High 31-54% (lowest for Co and Ni-rich) Moderate (412-584) Hexagonal Similar to Niccolite / Although Violarite appears similar, it is not zoned
Carrollite CuCo2S4 Creamy White / rare slight Pinkish tint None None >Chalcopyrite <Pyrite Anhedral Granular masses / Subhedral and Euhedral Octahedra Bornite Chalcocite Chalcopyrite Co-Pyrite Copper minerals Digenite Pyrrhotite Siegenite None Moderate to High 38-52% Cubic
Cassiterite
n
Cassiterite in PPL. 
Cassiterite in XP. NOte the internal reflections. 
SnO2 Brownish Gray C to Stannite, Wolframite, Ilmenite, Rutile, Magnetite: Brownish Gray Distinct / Gray to Brownish Gray Distinct Gray / in oil, masked by internal reflections <Pyrite Compact Anhedral masses / Zoned Subhedral to Euhedral crystals Twinning common / Cleavage may be visible Arsenopyrite Bismuth Bismuthinite Galena Hematite Magnetite Pyrite Pyrrhotite Rutile Sphalerite Stannite Wolframite Common / Yellow to Yellow-Brown (lighter than Sphalerite) Moderate 43% Very Hard (1168-1332) Tetragonal Similar to Sphalerite but is anisotropic and has lighter coloured internal reflections
Chalcocite
n
Chalcocite in PPL. 
Chalcocite in XP. 
Cu2S Blueish White C to Galena, Pyrite, Bornite, Copper: Blueish Gray to Blueish White / C to Covellite: White Very Weak Weak to distinct emerald Green to light Pinkish >Acanthite ~Digenite <Bornite Anhedral polycrystalline aggregates / vein fillings with Fe and Cu-Fe Sulphides (e.g. Bornite, Chalcopyrite, Digenite, Pyrite) Often in exsolution intergrowth with Bornite or low-temperature Cu- Sulphides Bornite Enargite Galena Sphalerite Stannite Tetrahedrite - Tennantite None Low 11% Extra Soft (84-87) Orthorhombic Often appears Isotropic, especially in supergene fine-grained aggregates
Chalcophanite Mn2O5•nH2O White to Gray Very strong and characteristic, especially in oil / White to Gray Very Strong / White to Gray Aggregates of tabular and radiating crystals / Colloform bands in secondary Mn-ores Perfect basal cleavage Filling veins in Mn-oxides e.g. Hausmannite Psilomelane Pyrolusite Zn-rich: deep Red / Otherwise None Moderate 32% Soft (188-253) Trigonal
Chalcopyrite
n
Chalcopyrite in PPL. 
Example of chalcopyrite disease. 
CuFeS2 Yellow to Brassy Yellow C to Pyrite: more Yellow / C to Gold: distinct Greenish tint Weak Weak but distinct / Gray-Blue to Yellow-Green ~Galena <Sphalerite Medium to coarse grained Anhedral aggregates / less commonly as well-developed Tetrahedra Twinning common / Basket weave exsolution with Bornite common / Can contain laths of Cubanite / Can contain “stars" of Sphalerite / Can contain “worms" of Mackinawite or Pyrrhotite Bornite Cubanite Digenite Galena Magnetite Pentlandite Pyrite Pyrrhotite Sphalerite Tetrahedrite None Low 9-27% Soft (187-203) Tetragonal Often alters along cracks and grain boundaries to Covellite
Chalcostibite CuSbS2 White with Pinkish Gray tint C to Silver, Galena, Grayish / C to Sphalerite: Pinkish Distinct in oil / Creamy to Brown Distinct / Pinkish to Greenish or Blueish Gray >Silver <Chalcopyrite <Sphalerite Anhedral grains / less commonly as Euhedral prismatic crystals Cleavage / Triangular pits may be visible / May be intergrown with Enargite Arsenopyrite Chalcocite Chalcopyrite Cinnabar Covellite Galena Jamesonite Pyrite Silver Sphalerite Tetrahedrite Rare / pale Red Moderate 45% Soft (283-309) Orthorhombic
Chromite
n
Chromite in PPL. 
(Fe,Mg)(Cr,Al)2O4 Dark Gray to Brownish Gray C to Magnetite, Sphalerite: darker / C to Ilmenite: less Brown-Red None Weak / Usually absent >Magnetite <Hematite Subhedral to Euhedral crystals / Coarse crystalline aggregates / Cataclastic effects common Zonal Textures with lighter (Fe-Rich) rims common Ilmenite Magnetite Millerite Pentlandite Platinum Pyrrhotite Common / Red Brown / None in Fe-rich samples Moderate 36-44% Very Hard (1278-1456) Cubic May have exsolution lamellae of Hematite, Ilmenite, Magnetite, Rutile, Ulvöspinel
Cinnabar HgS White with Blueish Gray tint C to Galena: darker, Blueish Distinct in oil Distinct / in oil often masked by internal reflections >Antimony <Galena <Pyrite Subhedral to Euhedral crystals / polycrystalline aggregates of Euhedral grains Bornite Cassiterite Chalcopyrite Enargite Galena Gold Marcasite Orpiment Pyrite Realgar Stibnite Tetrahedrite Intense and common / Red Low 13% Extra Soft to Soft (82-156) Trigonal Looks similar to Proustite and Pyrargyrite
Cobaltite
n
Cobaltite in PPL. 
(Co,Fe)AsS White with Pink or Violet tint C to Arsenopyrite: Pinkish / C to Pyrite: Whiter Weak / White to Pinkish Weak to distinct in oil / Blue-Gray to Brown >Skutterudite <Pyrite Euhedral crystals / Polycrystalline aggregates Twinning / Zoning / Cleavage Arsenopyrite Bismuth Chalcopyrite Gold Ni-Co Arsenides Niccolite Silver Uraninite None Low 24-30% Hard to Very Hard (935-1131) Orthorhombic (Pseudo-Cubic) Weak anisotropy makes Cobaltite distinct from Niccolite or Breithauptite
Coffinite U(SiO4)1-xOH)4x Gray Very Weak Very weak / Absent ~Pitchblende Euhedral Tetragonal crystals / Fine aggregates / Colloform bands Botryoidal encrustations and intergranular films, especially near organic matter Bismuth Loellingite Pitchblende Pyrite Rammelsbergite Sphalerite Uraninite Rare and weak in air / Common Brownish in oil High 51% Soft (230-302) Tetragonal
Cohenite Fe3C Creamy White C to Pyrrhotite: lighter Creamy / C to Iron: similar Weak but distinct Weak but distinct >Iron Irregular grains Twinning common in larger grains Graphite Kamacite Schreibersite Troilite None Low 8% Orthorhombic Rare on earth / Found in meteorites with 6-8 wt% Ni
Coltan / Columbite Tantalite (Fe,Mn)(Ta,Nb)2O6 Gray-White with Brown tint C to Magnetite: slightly less Brown Weak Distinct / Straight extinction Euhedral crystals / Anhedral aggregates May be Zoned / Cleavage may be visible May be within Cassiterite / May contain inclusions of Cassiterite Galena Hematite Ilmenite Rutile Uraninite Wolframite Common in Fe-rich / deep Red Low 15% Soft to Very Hard (240-1021) Orthorhombic Occurs as oriented intergrowths with Uraninite
Copper
n
Copper in PPL. Make sure the sample is well polished as copper tarnishes easily. 
Copper in XP. It is isotropic but scratches will appear anisotropic. 
Cu Pink / tarnishes Brownish C to Silver: Pink Weak Isotropic / Fine scratches will appear Anisotropic >Chalcocite <Cuprite Coarse to fine grained aggregates / Dendritic or spear-like crystals Lamellar Twinning visible if etched / Zoning due to Ag or As common Bornite Chalcocite Cuprite Enargite Iron Magnetite Pyrrhotite None High 65-92% Extra Soft (79-99) Cubic
Cosalite Pb2Bi2S5 White with Pink or Gray tint C to Galena: Yellowish to Green tint Weak to distinct Weak to Moderate / Pinkish Yellow, Blueish, Violet Gray >Galena Granular masses / Bundles of Subhedral Elongated Laths / Fibrous crystals No Twinning Arsenopyrite Bi and Sb Sulfosalts Bismuth Chalcopyrite Glaucodot Gold Pyrite Pyrrhotite Sphalerite Tetrahedrite Wolframite None Moderate 41-46% Extra Soft to Soft (74-161) Orthorhombic
Covellite
Covellite in PPL with strong pleochroism. 
Covellite in XP showing intense anisotropy. 
CuS Indigo Blue with Violet tint / Blueish White in Air Purple to Violet-Red to Blue-Gray in oil Strong to Extreme / Red-Orange to Brownish <Chalcopyrite Subhedral to Anhedral masses / Laths / Platelike crystals Bornite Chalcopyrite Digenite Enargite Pyrite Sphalerite Tennantite / May occur with Covellite None Low 4-24% Soft (128-138) Hexagonal Blaubleibender Covellite stays blue in oil, hence the name.
Cubanite CuFe2S3 Creamy Gray to Yellowish Brown C to Pyrrhotite: more Yellow, less Pink / C to Chalcopyrite: more Gray-Brown Grayish to Brownish Strong / Brownish to Blue >Chalcopyrite <Pyrrhotite Laths within coarse-grained Chalcopyrite / Irregular Granular aggregates Arsenopyrite Galena Mackinawite Magnetite Pentlandite Pyrrhotite Sphalerite None Moderate 35% Soft (247-287) Orthorhombic
Cuprite Cu2O Air: light Blueish Gray / Oil: darker / more Blue C to Chalcopyrite, Hematite: darker and Greenish Very Weak Strong / Anomalous Gray-Blue to Olive-Green >Chalcopyrite Euhedral octahedra / fine-grained mass Replaces Copper minerals Delafossite Goethite Marcasite Pyrite Tenorite Common / Deep Red characteristic Low 27% Soft (193-207) Cubic
Delafossite CuFeO2 Air: Yellow-Rose-Brown to Rose-Brown / Oil: Pinkish Gray to Brown-Gray C to Enargite, Tenorite: more Yellow Distinct Distinct to Strong / Blueish Gray / Straight extinction <Cuprite <Goethite Masses of subparallel crystals / Sheaf-like bundles / fine inclusions in Goethite Concentric and Botryoidal textures common Bornite Chalcocite Copper Covellite Cuprite Galena Goethite Limonite Pyrite Tennantite Tenorite None Low to Moderate 18-39% Moderate (412-488) Trigonal
Digenite Cu9S5 Grayish Blue C to Galena, Bornite: Blue / C to Chalcocite: darker Blue None Isotropic / Weakly anomalous ~Chalcocite ~Galena Irregular aggregates of Anhedral grains with lamellar intergrowths (with Cu-Sulphides or Bornite) Alters to Covellite Chalcopyrite Enargite Pyrite Tetrahedrite None Low 19% Extra Soft to Soft (86-106) Cubic
Dyscrasite Ag3Sb White C to Galena: Creamy White / C to Silver: slightly Grayer / C to Antimony: slightly Creamy Weak / White to Creamy White Weak to distinct >Galena >Silver <Chalcopyrite Euhedral Plate-like / Square crystals / Aggregates of Anhedral crystals Arsenic Cobaltite Galena Pyrite None High 60% Soft (153-179) Orthorhombic The “Dyscrasite" of Cobalt, Ontario, Canada is not Dyscrasite. It's Allargentum
Enargite Cu3AsS4 Pinkish Gray to Pinkish Brown / darker in Oil C to Bornite: Pinkish White / C to Chalcocite, Galena: Pinkish to Grayish Brown Distinct in oil: (//a) Grayish Pink (//b) Pinkish Gray (//c) Grayish Violet Strong / Blue, Green, Red, Orange >Galena >Chalcocite >Bornite ~Tennantite <Sphalerite Anhedral to Subhedral grains Cleavage / No Twinning Arsenopyrite Bornite Chalcocite Chalcopyrite Covellite Galena Pyrite Sphalerite Tennantite Rare / Deep Red Low 24% Soft (285-327) Orthorhombic
Famatinite Cu3SbS4 Pale Pinkish Orange C to Enargite: lighter Distinct to strong in oil / Orange-Brown to Grayish Violet Very Strong / Brown to Gray-Green >Bornite >Chalcopyrite ~Enargite <Sphalerite Anhedral to Euhedral grains Polysynthetic Twinning common / Star-shaped patterns may occur Bornite Chalcocite Chalcopyrite Enargite Galena Proustite Pyrargyrite Pyrite Sphalerite Tetrahedrite None Low 24% Soft (205-397) Tetragonal
Freibergite Ag-Tetrahedrite Gray / faint Yellow-Brown tint in Oil C to Proustite: Brownish / C to Galena: Grayish Brown / C to Sphalerite: lighter None Isotropic >Ag-sulfosalts <Galena <Sphalerite Irregular masses / inclusions of Anhedral crystals Argentite Bornite Chalcopyrite Co-Fe-Ni Arsenides Enargite Galena Proustite Silver Rare / Brownish Red when visible Moderate 32% Soft (263-340) Cubic
Galena
n
Galena in PPL. Note the triangular pits. 
PbS White / sometimes with Pink tint C to Sphalerite: White / C to Tennantite: Pinkish None Isotropic / Weakly anomalous >Proustite ~Chalcopyrite <Tetrahedrite Anhedral masses / Euhedral cubes Perfect cleavage usually visible / Triangular pits Often contains inclusions of Chalcopyrite Pb-Bi and Pb-Sb Sulfosalts Silver Sphalerite Tetrahedrite / May occur as inclusions in Chalcopyrite Sphalerite None Moderate 42% Extra Soft (59-65) Cubic
Gersdorffite NiAsS White with Yellow or Pink tint C to Skutterudite: more Yellow / C to Linnaeite: less Pink / C to Niccolite: Blueish None Isotropic / Weakly anomalous >Linnaeite ~Loellingite <Pyrite Euhedral crystals Cleavage common / may show zonal growth Bismuth Bornite Chalcopyrite Cobaltite Niccolite Pyrite Silver Skutterudite Uraninite None High 54% Hard (844-935) Cubic Sometimes occurs as pseudoeutectic intergrowths with Niccolite, Maucherite, Pyrrhotite, Chalcopyrite
Glaucodcot (Co,Fe)AsS White to light Cream C to Arsenopyrite: more Blueish White Weak / Weaker than Arsenopyrite Distinct / less than for Arsenopyrite <Arsenopyrite <Cobaltite Subhedral to Euhedral crystals Often with inclusions Arsenopyrite Cobaltite Galena Niccolite Pyrite Rammelsbergite Safflorite Skutterudite None Moderate 50% Very Hard (1097-1115) Orthorhombic
Goethite FeO•OH Gray with Blueish tint C to Sphalerite: more Blueish / C to Hematite: darker / C to Lepidocrocite: darker Weak in air; distinct in oil but often masked by internal reflections Distinct / Gray-Blue, Gray-Yellow, Brownish ~Lepidocrocite <Magnetite <Hematite Porous Colloform bands with radiating Fibrous texture / Porous pseudomorphs after Pyrite Nearly always secondary as veins, fracture fillings, or Botryoidal coatings Chalcopyrite Galena Hematite Lepidocrocite Mn-Oxides Pyrite Pyrite Pyrrhotite Sphalerite Common / Brownish Yellow to Reddish Brown Low 15% Moderate (667) Orthorhombic Internal reflection colours helps differentiate Goethite and Lepidocrocite
Gold
n
Gold in PPL. The high reflectivity makes the image look a bit washed out. 
Au Bright Golden Yellow C to Chalcopyrite: no Greenish tint None Isotropic / Incomplete extinction >Galena <Tetrahedrite <Chalcopyrite Isolated grains / small veins Arsenopyrite Chalcopyrite Pyrite None High 77-88% Extra Soft (53-58) Cubic Addition of Silver to form Electrum changes color to whitish and increases reflectivity
Graphite
Graphite in PPL. Note how it occurs as isolated laths. 
Graphite in XP. 
C Brownish Gray to Grayish Black C to Molybdenite: darker Very strong / Brownish Gray to Grayish black Very Strong / straw Yellow to Brown or Violet Gray <Almost all minerals small Plates / isolated Laths / bundles of blades Basal cleavage may be visible / Undulose Extinction common Inclusions in Magnetite Pyrite Pyrrhotite Sphalerite None Low 6-27% Extra Soft (42705) Hexagonal Much more common than Molybdenite
Hausmannite Mn3O4 Blueish to Brownish Gray C to Jacobsite: Grayer / C to Bixbyite: darker / C to Braunite: less Brown Very distinct in oil / Blueish Gray to Brownish Gray Strong / Yellow Brown to Blueish Gray >Manganite >Pyrolusite <Jacobsite <Bixbyite <Braunite Coarse-grained equigranular Anhedral crystals / often in veinlets Irregular Twinning / alters to Pyrolusite and Psilomelane Mn-Oxides Common / Blood Red, especially in oil Low 16% Moderate (437-572) Tetragonal
Hematite
n
Hematite in PPL. 
Hematite in XP. 
α-Fe2O3 Gray C to Ilmenite, Magnetite: White / C to Pyrite: Blueish Gray / C to Goethite, Lepidocrocite: White Weak Distinct / Gray-Blue, Gray-Yellow >Magnetite <Pyrite Bladed or Needle-like subparallel radiating aggregates Lamellar Twinning / Exsolution lenses or lamellae common in Ilmenite or Magnetite Bornite Cassiterite Chalcopyrite Magnetite Pyrite Rutile Sphalerite Umenite Common / Deep Red Low 25-30% (1000-1100) Hexagonal
Idaite Cu5FeS6 to Cu3FeS4 Reddish Orange / Red-Brown to Yellowish Gray Strong Reddish Orange / Red-Brown to Yellowish Gray Strong to Extreme /Green or Gray-Green >Covellite Tabular crystals with Covellite, Pyrite, or Bornite if Hypogene / Lamellae and veinlets in Bornite if Supergene Bornite Covellite Pyrite None Low to Moderate 27-34% Soft (176-260) Tetragonal
Ilmenite
n
Ilmenite in PPL. Note the hematite exsolution which is common. 
Ilmenite in XP. 
FeTiO3 Brownish with Pink or Violet tint C to Magnetite: darker, Brownish Distinct / Pinkish Brown / dark Brown Strong / Greenish Gray to Brownish Gray >Magnetite <Hematite Subhedral to Anhedral grains / Exsolution lamellae or lenses in Hematite or Magnetite Lamellar Twinning Chromite Hematite Magnetite Pentlandite Pyrite Pyrrhotite Rutile Tantalite Rare / dark Brown Low 16% Moderate (566-698) Trigonal
Iron Fe White / slight Blueish or Yellowish C to Pentlandite: much Whiter / C to Cohenite: slightly Blueish None Isotropic <Troilite <Magnetite <Cohenite Irregular patches / drop-like grains in stony meteorites Intergrowths of γ-Fe and α-Fe form Widmanstät;ten structures which are brought out by etching / Oxidizes to Hematite, Goethite, Lepidocrocite Chromite Copper Ilmenite Schreibersite Troilite None High 58% Soft (110-117) Cubic
Jacobsite (Fe,Mn)2O4 Rose Brown to Brownish Gray C to Magnetite, Braunite: Olive-Green / C to Hausmannite: less Gray / C to Bixbyite: Olive-Gray None Isotropic / Weakly anomalous ~Magnetite <Braunite Anhedral grains / rounded Subhedral crystals Alters to other Fe-Mn minerals Occurs with and/or alters to Goethite Hematite Psilomelane Pyrolusite Common / Deep Red, especially when Mn-rich Low 21% Hard (720-813) Cubic
Jamesonite Pb4FeSb6S14 White C to Galena: similar or slightly Greenish / C to Stibnite: lighter Strong / White to Yellow Green Strong / Gray, Tan, Brown, Blue <Galena Needle or Lath-like crystals / Bundles Cleavage parallel to long dimension / Twinning Arsenopyrite Boulangerite Chalcopyrite Galena Pyrargyrite Pyrite Sphalerite Tetrahedrite Reddish in Bi-Jamesonite Moderate 36-44% Extra Soft (66-86) Monoclinic
Kamacite α-Fe α-Fe α-Fe contains < ~6% Ni and is slightly Blueish C to Pentlandite: much Whiter / C to Cohenite: slightly Blueish None Isotropic Fine exsolution of Cohenite occurs in α-Fe Intergrowths of γ-Fe and α-Fe form Widmanstät;ten structures which are brought out by etching / Oxidizes to Hematite, Goethite, Lepidocrocite Chromite Copper Ilmenite Schreibersite Troilite None High 58% Soft (110-117) Cubic Found in Iron meteorites / Rare on earth / cf. Iron
Kobellite Pb2(Bi,Sb)2S5 White C to Galena: slightly darker Distinct / Greenish White to Violet-Gray Distinct / Gray to Gray-Brown >Bismuth <Galena Granular to tabular aggregates Well developped cleavage / Twinning / Intergrowths with Tetrahedrite Arsenopyrite Bismuth Bismuthinite Chalcopyrite Pyrite Pyrrhotite None Moderate 44% Extra Soft to Soft (100-117) Orthorhombic
Lepidocrocite γ-FeO•OH Grayish White C to Goethite: lighter and Whiter / C to Hematite: Greenish tint Weak to distinct Strong/ Gray <Goethite Occurs in Crusts and veinlets / Porous pseudomorphs Common / Reddish Low 11-18% Moderate (402) Orthorhombic Internal reflection colours helps differentiate Goethite and Lepidocrocite / From the weathering Iron oxides and sulphides
Linnaeite Co3S4 Creamy White C to Skutterudite: Grayish White / C to Ullmanite, Gersdorffite: Creamy or Yellowish None Isotropic >Chalcopyrite >Sphalerite <Pyrite Euhedral crystals / Subhedral aggregates May have lamellar intergrowths with associated minerals Bismuth Bornite Chalcopyrite Covellite Millerite Niccolite Pyrite Pyrrhotite Safflorite None Moderate 50% Moderate (450-613) Cubic
Loellingite FeAs2 White with Yellowish tint C to Arsenopyrite: less Yellow / C to Rammelsbergite, Safflorite: similar Weak but distinct / Blueish White to Yellowish White Very Strong / Orange-Yellow, Red-Brown, Blue, Green >Chalcopyrite >Sphalerite <Arsenopyrite Interlocking to radiating aggregates of Euhedral crystals / Sometimes as skeletal crystals Twinning common Antimony Arsenic Arsenides Arsenopyrite Chalcopyrite Dyscrasite Galena Uraninite None High 52% Hard (859-920) Orthorhombic
Mackinawite Fe1+xS Pinkish to Reddish Gray C to Pyrrhotite: similar Distinct to Strong / Pinkish tray to Gray Very Strong / Grayish White, Blueish, Brownish ~Pyrrhotite Small worm-like grains / Lamellae / less commonly as small Plates Most easily found as bright grains under nearly crossed polars Chalcopyrite Cubanite Pentlandite Pyrrhotite None Low to Moderate 16-43% Extra Soft to Soft (74-181) Tetragonal Valleriite's anisotropy has a more pronounced orange tint
Maghemite γ-Fe2O3 Blueish Gray C to Goethite: Gray, lighter / C to Hematite: Blueish Gray / C to Magnetite: Blueish None Isotropic >Magnetite <Hematite Lamellae / porous patches Forms as a rare oxidation product of Magnetite Rare / Brownish Red Low 23% Moderate (412) Cubic
Magnetite
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Magnetite in PPL. 
Fe3O4 Gray with Brownish tint C to Hematite: darker Brown / C to Ilmenite: less Pink / C to Sphalerite: lighter None Isotropic / Weakly anomalous >Pyrrhotite <Ilmenite <Hematite <Pyrite Euhedral / Subhedral / Octahedral Grains / skeletal crystals / Anhedral polycrystalline aggregates Often contains exsolution or oxidation lamellae of Hematite Ilmenite and ulvöspinel / Alters to Hematite and Goethite Bornite Chalcopyrite Galena Pentlandite Pyrite Pyrrhotite Sphalerite None Low 20% Moderate to Hard (681-792) Cubic
Manganite MnO(OH) Gray to Brownish Gray C to Pyrolusite: darker Gray Weak / Brownish Gray Strong / Yellow, Blueish Gray, Violet-Gray <Hausmannite <Jacobsite Prismatic to Lamellar crystal aggregates Cleavage / Twinning / often intergrown with Pyrolusite and Psilomelane Braunite Goethite Hausmannite Common / Blood Red Low 14-21% Moderate to Hard (630-743) Monoclinic
Marcasite
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Marcasite in PPL. 
Marcasite in XP. 
FeS2 Yellowish White with slight Pinkish or Greenish tint C to Pyrite: Whiter / C to Arsenopyrite: Greenish Yellow Strong / Brownish to Yellowish Green Strong / Blue, Green-Yellow, Purple-Gray ~Pyrite Subhedral / Lamellar intergrowths with Pyrite in Euhedral crystals / Radiating Colloform bands Twinning Pyrite and other common Sulphides None Moderate to High 49-56% Very Hard (1288-1681) Orthorhombic Forms as hypogene crystals and as supergene veinlets in Pyrrhotite and Iron oxides
Maucherite Ni11As8 White C to Cobaltite: similar / C to Loellingite: Brownish Gray / C to Breithauptite: Blueish Gray None Weak to distinct in oil / Gray >Chalcopyrite >Sphalerite <Safflorite <Loellingite Euhedral crystals / Anhedral aggregates Twinning / May be intergrown with Niccolite or Gersdorffite Chalcopyrite Cubanite Siegenite None Moderate 48% Moderate to Hard (623-724) Tetragonal
Mawsonite Cu7Fe2SnS10 Brownish Orange Strong / Orange to Brown Very Strong / Straw-Yellow to Royal Blue >Bornite Irregular inclusions Inclusion in Bornite Chalcocite Chalcopyrite Enargite Galena Pyrite Stannite Tetrahedrite None Low to Moderate 27-35% Soft (166-210) Tetragonal
Miargyrite AgSbS2 in Air: White / in Oil: Blueish tint C to Galena: darker with Green-Gray tint / C to Freibergite: Blueish / C to Pyrargyrite: Whiter Moderate / White to Blueish Gray Strong / Blue-Gray to Brownish / masked by internal reflections >Pyrargyrite <Stephanite <Galena Granular Anhedral aggregates Twinning Galena Polybasite Pyrargyrite Silver Sphalerite Stephanite Tetrahedrite Common / Deep Red Low to Moderate 30-35% Extra Soft to Soft (88-130) Monoclinic
Millerite NiS Yellow C to Chalcopyrite: lighter, not Greenish / C to Linnaeite, Pentlandite: Yellower Distinct in oil / Yellow to Blue or Violet Strong / Lemon-Yellow to Blue or Violet >Chalcopyrite <Pentlandite Radiating aggregates / Anhedral Granular masses Twinning / Cleavage/ common as oriented intergrowths with Linnaeite, Violarite, Pyrrhotite Ni-bearing Sulphides often as replacement or alteration None Moderate to High 50-59% Soft (192-376) Trigonal
Molybdenite
Molybdenite in PPL. 
Molybdenite in XP. 
MoS2 White to Gray with Blueish tint C to Graphite: lighter Strong to Extreme Very Strong / White with Pinkish tint / dark Blue if polars not comptetely crossed <Almost all minerals Small deformed Plates / Irregular inclusions / Less commonly as Rosettes or Colloform bands Cleavage / Twinning / Undulose extinction / Often in veins Bismuth Bismuthinite Bornite Cassiterite Chalcopyrite Pyrite Sulphides Wolframite None Low to Moderate 19-39% Extra Soft (8-100) Trigonal
Niccolite (nickeline)
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Niccolite in PPL. 
Niccolite in XP. 
NiAs Yellowish Pink to Brownish Pink C to Maucherite, Skutterudite, Bismuth, Arsenic: more Pink / C to Breithauptite: Pinkish Yellow Strong Very Strong / Yellow, Greenish Violet-Blue, Blue-Gray >Chalcopyrite >Breithauptite <Skutterudite <Pyrite Isolated Subhedral and Euhedral crystals / Anhedral aggregates / Concentric bands / Complex intergrowths (with Pyrrhotite, Chalcopyrite, Maucherite) Commonly intergrown with Arsenides / Often twinned and in radial aggregates Intergrowths with Chalcopyrite Maucherite Pyrrhotite None Moderate to High 46-56% Soft (363-372) Hexagonal
Orpiment As2S3 Gray C to Realgar: slightly lighter / C to Sphalerite: lighter Strong in Air: (//a) White; (//b) dull Gray / Reddish: (//c) dull Gray-White / in Oil: (//a) Gray-White; (//b) dark Gray; (//c) Gray-White Strong / in oil masked by internal reflections >Realgar Tabular interlocking Anhedral masses / Needle or Lath-like crystals Often formed on Realgar Arsenic Arsenopyrite Enargite Loellingite Pyrite Realgar Sphalerite Stibnite Common and intense / White to Yellow Low 22-28% Extra Soft (22-58) Monoclinic
Para rammelsbergite NiAs2 Whiter than associated Co-Ni-Fe Arsenides Very Weak to distinct / Yellowish to Blueish White Strong / less than Rammelsbergite and without Blue >Niccolite <Skutterudite Tabular crystals with rectangular outlines / Mosaics of intergrown crystals May be zoned / Twinning rare Cobaltite Gersdorffite Niccolite Proustite Pyrite Rammelsbergite Silver Skutterudite None High 59% Moderate to Hard (681-830) Orthorhombic Solid solution with Polybasite
Pearcite Ag16As2S11 Gray C to Pyrargyrite: darker Brownish / C to Tetrahedrite: similar Air: Weak; oil: distinct / Green to Gray with Violet tint Blue, Gray, Yellow-Green, Brown / Air: Moderate / Oil: Strong >Argentite ~Pyrargyrite <Stephanite Platelike to equant grains With, or in, Galena Pyrite Sphalerite Tetrahedrite Common / Deep Red Low 29% Soft (180-192) Monoclinic
Pentlandite
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Pentlandite in PPL. Note the subtle colour difference between the background Pyrrhotite. 
Pentlandite in XP. 
(Fe,Ni)9S8 Light Creamy to Yellowish C to Pyrrhotite: lighter / C to Linnaeite: darker, not Pinkish None Isotropic >Chalcopyrite <Pyrrhotite Granular veinlets / “flames" / lamellae in Pyrrhotite or Chalcopyrite Alters to Violarite and Millerite along cracks and grain boundaries Cubanite Mackinawite Magnetite Pyrite None Moderate 47% Soft (268-285) Cubic
Platinum Pt White None Isotropic / Incomplete extinction >Sphalerite <Pyrrhotite Isolated Euhedral to Subhedral crystals May be zoned / exsolution Laths of Iridium and Osmium Chalcopyrite Chromite Magnetite Pentlandite Pyrrhotite None High 70% Soft (297-339) Cubic May occur with other small grains of Platinum minerals
Polybasite Ag16Sb2S11 Gray C to Galena: darker / C to Pyrargyrite: darker Brownish / C to Tetrahedrite: similar Air: Weak; oil: distinct / Green to Gray with Violet tint Blue Gray, Yellow-Green, Brown / Air: moderate / Oil: Strong >Argentite ~Pyrargyrite <Stephanite Forms complete solid solution with Pearcite Complete solid solution with Pearcite Common / Deep Red Low 30% Soft (108-141) Monoclinic Similar occurrences as Pearcite
Proustite Ag3AsS3 Blueish Gray C to Pyrargyrite: darker Distinct / Yellowish to Blueish Gray Strong / masked by internal reflection ~Pyrargyrite Forms complete solid solutions with Pyrargyrite Complete solid solutions with Pyrargyrite Always / Scarlet Red Low 23-28% Extra Soft to Soft (70-105) Trigonal Same characteristics as Pyrargyrite except that Proustite occurs in more As-rich environments
Psilomelane (General name for massive, hard manganese oxides) BaMn2+Mn4+8O16(OH)4 Blueish Gray to Grayish White C to Pyrolusite: darker / C to Braunite, Manganite, Jacobsite, Hausmannite, Bixbyite: lighter Strong / White to Blueish Gray Strong / White to Gray Very fine acicular crystals in concentric layers / Botryoidal masses Often intergrown with Pyrolusite and Cryptomelane Mn-Oxides Rare / Brown Low 15-30% Soft to Hard (203-813)
Pyrargyrite Ag3SbS3 Blueish Gray C to Proustite: slightly lighter / C to Galena: Grayish Blue Distinct to Strong Strong / Gray to dark Gray / in oil, masked by internal reflections >Polybasite <Galena Irregular grains / Aggregates Twinning / Zonal Textures Arsenopyrite Chalcopyrite Galena Ni-Co-Fe Arsenides Pyrite Sb-sulfosalts Sphalerite Tetrahedrite Common / Intense Red Low 27% Soft (107-144) Trigonal Solid solution with Proustite
Pyrite
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Pyrite in PPL. 
FeS2 Yellowish White C to Marcasite: Yellower / C to Arsenopyrite: Creamy Yellow / C to Chalcopyrite: lighter None Often Weak / Blue-Green to Orange-Red >Arsenopyrite >Marcasite <Cassiterite Euhedral cubes and pyritohedra / Anhedral crystalline masses / Colloform bands of very fine grains Growth zoning / Twinning Super common, occurs with most ore minerals None High 52% Very Hard (1505-1620) Cubic The most abundant Sulphide ™
Pyrolusite MnO2 Creamy White C to Magnetite, Hematite: Yellowish / C to Manganite: White Distinct in oil / Yellowish White to Gray-White Very Strong / Yellowish, Brownish, Blue Very variable depending on grain size and orientation Coarse-grained tabular crystals / banded aggregates Cleavage / Twinning / Very fine grained material may be intergrown with Psilomelane, Hematite, Fe-hydroxides Bixbyite Braunite Magnetite Manganite None Low to Moderate 28-40% Soft (146-243) Tetragonal
Pyrrhotite (Hexagonal)
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Pyrrhotite in PPL. Note the subtle pink-ish colour compared to the neighbouring chalcopyrite. 
Anisotropic pyrrhotite surrounding an isotropic pentlandite in XP. 
Fe1-xS / (~Fe9S10) Creamy Pinkish Brown C to Pentlandite: darker / C to Cubanite: more Pinkish Very distinct / Creamy Brown to Reddish Brown Very Strong / Yellow-Gray, Grayish Blue >Chalcopyrite ~Pentlandite <Pyrite Anhedral Granular masses Twinning common, especially where stressed / Lamellar exsolution intergrowths of hexagonal and monoclinic forms common / Weathering of hexagonal Pyrrhotite yields a rim of monoclinic Pyrrhotite (usually slightly lighter in colour) Most other common Sulphides None Moderate 36% Soft (230-259) Hexagonal Pentlandite exsolution lamellae and flames common in Ni-ores / often contains Mackinawite lamellae
Pyrrhotite (Monoclinic)
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Pyrrhotite in PPL. Note the subtle pink-ish colour compared to the neighbouring chalcopyrite. 
Anisotropic pyrrhotite surrounding an isotropic pentlandite in XP. 
(~Fe7S8) Creamy Pinkish Brown C to Pentlandite: darker / C to Cubanite: more Pinkish Very distinct / Creamy Brown to Reddish Brown Very Strong / Yellow-Gray, Grayish Blue >Chalcopyrite ~Pentlandite <Pyrite Anhedral Granular masses Twinning common, especially where stressed / Lamellar exsolution intergrowths of hexagonal and monoclinic forms common / Weathering of hexagonal Pyrrhotite yields a rim of monoclinic Pyrrhotite (usually slightly lighter in colour) Most other common Sulphides None Moderate 36-42% Soft to Moderate (373-409) Monoclinic
Rammelsbergite NiAs2 White more so than other Ni-Co-Fe Arsenides Very Weak in air; distinct in oil / Yellowish to Blueish Strong / Pinkish, Brownish, Greenish, Blueish ~Skutterudite <Safflorite <Loellingite Fine-grained aggregates of interlocking crystals / Zoning / Spherulitic radiating textures / Fibres Simple or complex Twinning / May be intergrown with Niccolite and Co-Ni-Fe Arsenides / Sometimes as overgrowths on dendrites of Silver or Bismuth Bismuth Co-Ni-Fe Arsenides Niccolite Silver None High 57% Moderate to Hard (630-758) Orthorhombic Similar to Safflorite
Realgar As4S4 or AsS Dull Gray C to Sphalerite: similar / C to Cinnabar: darker / Orpiment slightly darker Weak but distinct / Gray with Reddish to Blueish tint Strong / in oil masked by internal reflections <Orpiment Irregular / Plate-like masses with Orpiment Arsenic Arsenopyrite As-sulfosalts Enargite Proustite Pyrite Stibnite Tennantite Common and intense / Yellowish Red Low 21% Extra Soft (47-60) Monoclinic
Rutile TiO2 Gray / faint Blueish tint C to Magnetite, Chromite: similar / C to Ilmenite: no Brownish tint / C to Cassiterite: lighter Distinct Strong / masked by internal reflections >Ilmenite <Hematite Euhedral to Subhedral / Needlelike Common in hydrothermally altered rocks Ilmenite Tantalite Ti-Hematite Ti-Magnetite Common and intense / White, Yellowish, Reddish Brown Low 19% Hard (894-974) Tetragonal
Safflorite (Co,Fe,Ni)As2 White with Blueish tint C to Bismuth: Blueish / C to Silver: Grayish White Very Weak / Blueish to Gray Strong >Skutterudite <Loellingite Concentric layers of Radiating masses of Anhedral to Subhedral crystals / Euhedral crystals / Starlike triplets Twinning common Other Arsenides None High 54% Hard (792-882) Orthorhombic
Scheelite CaWOs4 Gray-White / darker in Oil C to Gangue: similar in air / lighter in oil None Distinct / masked by internal reflections <Wolframite Equant to Lath-like polycrystalline aggregates / Partial replacement of Wolframite Fluoresces pale blue to yellow under UV light / Intergrown with Fe-oxides, Huebnerite, Ferberite, Cassiterite Intergrown with Cassiterite Fe-oxides Ferberite Huebnerite Common / White High 54% Soft to Moderate (383-464) Tetragonal
Schreibersite (Fe,Ni)3P in Air: White / in Oil: Brownish Pink tint C to Cohenite: lighter / C to Iron: similar In oil distinct / Pinkish Brown to Yellowish Weak but distinct in oil >Cohenite ~Iron Oriented Needle and tablet-like inclusions in Iron meteorites Inclusions in Iron in meteorites None Low 10% Soft (125) Tetragonal
Siegenite (Co,Ni)3S4 Creamy White with slight Pink tinge C to Cattierite: less Pinkish None lsotropic ~Linnaeite Euhedral and Subhedral crystals / Anhedral polycrystalline aggregates Cattierite Pyrite Uraninite Vaesite None Moderate 47% Moderate (459-548) Cubic
Silver Ag Bright White with Creamy tint / tarnishes rapidly C to Antimony, Arsenic: brighter and Creamy None Isotropic / Fine scratches often look Anisotropic >Proustite >Galena <Tetrahedrite Irregular masses / veinlets / Inclusions / Dendrites within Arsenides Lamellar intergrowths with Allargentum / Incomplete extinction / Tarnishes rapidly Ag-sulfosalts Argentite Co-Fe-Ni Arsenides Cu-Sulphides Galena None High 93% Extra Soft (60-65) Cubic
Skutterudite
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Skutterudite in PPL with characteristic "teeth". 
(Co,Ni)As2-3 Cream-White to Grayish White / often in zones C to Cobaltite: White / C to Safflorite: Yellowish None Isotropic / sometimes weakly anomalous >Linnaeite <Arsenopyrite <Pyrite ~Safflorite Characteristically radial blade-like crystals with well-developed growth zoning / Euhedral single crystals May be intergrown with Niccolite Bismuth other Co-Fe-Ni Arsenide Intergrowth with Bismuth Niccolite None High 55% Moderate to Hard (606-824) Cubic Occurs in Ag-Bi-U rich deposits
Sphalerite
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Sphalerite in PPL. 
Sphalerite in XP. Note the internal reflections. 
(Zn,Fe)S Gray / sometimes with Brown tint C to Magnetite: darker None Isotropic / sometimes weakly anomalous >Chalcopyrite >Tetrahedrite <Pyrrhotite <Magnetite Irregular Anhedral masses Growth zoning of light and dark bands / Often featureless except for internal reflections / Commonly contains inclusions of Chalcopyrite, Pyrrhotite, Galena, and less commonly, Stannite Chalcopyrite Galena Pyrite Pyrrhotite Common / Yellow-Brown to Reddish Brown Low 16% Soft (138-160) Cubic Internal reflections and the lack of cleavage allows you to distinguish from Magnetite
Stannite Cu2FeSnS4 Brownish Olive-Green C to Tetrahedrite: darker Brownish Gray / C to Sphalerite: lighter, Yellow-Brown to Olive-Green Distinct / light Brown to Brown-Olive-Gray Moderate / Yellow-Brown, Olive-Green, Violet-Gray >Chalcopyrite >Tetrahedrite <Sphalerite Anhedral grains / Granular aggregates / oriented intergrowths with Chalcopyrite, Sphalerite and Tetrahedrite Cleavage / compound Twinning, sometimes in microline pattern Bismuth Chalcopyrite Sphalerite Tetrahedrite Tungsten None Low 26% Soft (140-326) Tetragonal Common with Bismuth and Tungsten minerals / In many ore types as a minor phase
Stephanite Ag5SbS4 Gray with Pinkish Violet tint C to Galena: darker, Pinkish / C to Polybasite, Pyrargyrite: lighter Weak but distinct / Gray to Pinkish Gray Strong in oil / Violet to Green >Polybasite >Pyrargyrite <Tetrahedrite Anhedral aggregates / Euhedral columnar crystals Compound Twinning common Arsenides Ni-Co-Fe Sulfosalts Silver None Low 28% Extra Soft to Soft (26-124) Orthorhombic
Stibnite
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Stibnite in PPL. 
Stibnite in XP. 
Sb2S3 White to Grayish White C to Bismuthinite: darker / C to Antimony: Grayish Strong / Grayish White to White Very Strong / often undulose / Blue, Gray, Brown, Pinkish Brown >Orpiment <Chalcopyrite Granular aggregates / Lath-like crystals often with deformation textures Pressure Twinning / Undulose Extinction / Deformation textures Chalcopyrite Pyrite Pyrrhotite Sphalerite None Low to Moderate 30-48% Extra Soft to Soft (48-153) Orthorhombic
Stromeyerite AgCuS Gray with Violet Pinkish tint C to Chalcocite: Lavender-Gray Weak but distinct in oil / Gray-Brown to light Gray with Blue or Pink tint Strong / Light Violet, Purple, Brown, Orange-Yellow <Galena <Chalcocite Hypogene phase in Granular aggregates / Supergene phase in small veinlets Often intergrown with other Silver numerals Cu-Fe and Fe Sulphides Silver Sphalerite None Low to Moderate 26-31% Extra Soft (30-32) Orthorhombic
Sylvanite (Au,Ag)Te2 Creamy White C to Galena: lighter Distinct / Creamy White to Brownish Strong / light Blueish Gray to dark Brown >Argentite <Pyrargyrite Skeletal blades Well-developed cleavage / characteristic polysynthetic twinning / Often intergrown with other Gold-Tellurides Argentite Bornite Chalcopyrite Galena Gold Pyrite Sphalerite None High 53-63% Soft (154-172) Monoclinic
Taenite γ-Fe γ-Fe contains ~ 27-60% Ni and is slightly Yellowish C to Pentlandite: much Whiter / C to Cohenite: slightly Blueish None Isotropic Intergrowths of γ-Fe and α-Fe form Widmanstät;ten structures which are brought out by etching / Oxidizes to Hematite, Goethite, Lepidocrocite Chromite Copper Ilmenite Schreibersite Troilite None High 58% Soft (110-117) Cubic Found in Iron meteorites / Rare on earth / cf. Iron
Tennantite
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Tennantite in PPL. 
Cu12As4S13 (May contain Fe, Zn, Sb etc,) Gray / sometimes with Greenish or Blueish tint C to Galena, Chalcocite: Greenish / C to Pearcite: similar None Isotropic >Galena >Chalcopyrite <Sphalerite Occurrences the same as for Tetrahedrite except in more As-rich envIronments Complete solid solution with Tetrahedrite Common / Reddish Low 29% Soft (294-380) Cubic
Tenorite CuO in Air: Gray to Gray-White / in Oil: strongly pleochroic C to Cuprite: Brownish Blueish / C to Chalcocite: Brownish / C to Goethite: lighter Yellowish Distinct Strong / Blue to Gray >Chalcocite <Goethite<Cuprite Aggregates of acicular crystals / concentrically grown aggregates May have Lamellar Twinning Cu and Fe oxides in weathering zone None Low 20-28% Soft (190-300) Monoclinic
Tetradymite Bi2Te2S White with Creamy tint C to Chalcopyrite: lighter / C to Galena: Yellowish Weak Distinct / Blueish Gray to Yellow Gray >Bismuth <Galena Tabular Plates / Granular aggregates Basal cleavage common / Twinning rare / Intergrowths with Telluro-Bismuthinite Galena Gold Pb-Bi Sulfosalts None High 55-61% Extra Soft (25-76) Trigonal
Tetrahedrite Cu12SbS13 (May contain Fe, Zn, Ag, As, Hg etc.) Gray with Olive or Brownish tint C to Galena: Brownish or Greenish / C to Chalcocite: Blue-Gray / C to Sphalerite: lighter None Isotropic >Galena ~Chalcopyrite <Sphalerite (Hardness varies with composition) Irregular masses of Anhedral grains interstitial to Fe and Cu-Fe sulphides / Rounded inclusions in Galena and Sphalerite Forms complete solid solution with Tennantite / Growth zoning especially in more As-rich members Arsenopyrite Galena Sphalerite Rare / Increasingly common as As-content increases / Reddish Moderate 32% Soft (312-351) Cubic
Troilite FeS is Troilite Creamy Pinkish Brown C to Pentlandite: darker / C to Cubanite: more Pinkish Very distinct / Creamy Brown to Reddish Brown Very Strong / Yellow-Gray, Grayish Blue >Chalcopyrite ~Pentlandite <Pyrite Anhedral equigranular masses with Iron Occurs in meteorites Most other common Sulphides None Moderate 39% cf. Pyrrhotite
Ullmannite NiSbS White with Blueish tint C to Gersdorffite: less Yellow / C to Skutterudite: more Yellow / C to Linnaeite: White None Isotropic >Linnaeite ~Gersdorffite <Pyrite Dispersed Subhedral to Euhedral crystals Cleavage may be visible / Triangular cleavage pits Arsenides Cu-Fe Sulphides Co-Fe-Ni Antimonides None Moderate 47% Moderate (592-627) Cubic
Ulvöspinel Fe2TiO4 Brown to Reddish Brown C to Magnetite: darker Brown None Isotropic >Magnetite Very fine dark isotropic exsolution lamellae / Less commonly as octahedral crystals / Matrix containing oriented cubes of Magnetite Very fine, dark isotropic exsolution lamellae in Ti-Magnetite, giving a “doth weave" texture Ilmenite Magnetite None Low 15% (-650) Cubic
Uraninite UO2, usually partly oxidised Brownish Gray C to Magnetite: Less Pink / C to Sphalerite: Brownish None Isotropic >Magnetite <Pyrite Colloform / Oolitic / Dendritic masses Growth-zoning / Twinning common / Cleavage may be visible / May contain inclusions of Gold Cu-Fe Sulphides Pyrite Uranium minerals Common / Dark Brown to Reddish Brown Low 14% Moderate (499-548) Cubic
Valleriite (Fe,Cu)S2 (Mg,Al)(OH)2 Bronze to Gray Very Strong Strong to Extreme / White to Gray-bronze with satin-like texture >Chalcopyrite ~Cubanite <Pyrrhotite Veinlets / Interstitial fillings / Small inclusions within and surrounding Chalcopyrite ,Magnetite, Pentlandite andPyrrhotite Bronze anisotropy appears in a satin-like wavy pattern Chalcopyrite Magnetite Pentlandite Pyrrhotite None Low 10-23% Extra Soft (30) Hexagonal Mackinawite has a sharper extinction and less of an orange anisotropism
Violarite FeNi2S4 Brownish Gray with Violet tint C to Pentlandite: darker, Violet tint / C to Pyrrhotite: lighter / C to Millerite: Brownish Violet None Isotropic >Chalcopyrite >Sphalerite ~Pentlandite <Pyrrhotite Porous alteration product along grain boundaries and fractures / Equant Anhedral grains Sometimes as fine lamellar intergrowths with Millerite and Chalcopyrite / Porous alteration product along grain boundaries and fractures of Pentlandite, Pyrrhotite, and Millerite / Equant Anhedral grains with Pyrite, Millerite Pyrrhotite Millerite Pentlandite Pyrite Pyrrhotite None Moderate 45% Soft (241-373) Cubic
Wolframite / Ferberite - Hübnerite Series
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Wolframite in PPL. 
Wolframite in XP. 
(Fe,Mn)WO4 Air: Gray to White / Oil: Gray with Brown or Yellow tint C to Sphalerite: similar / C to Magnetite: darker / C to Cassiterite: lighter Weak Weak to distinct / Yellow to Gray >Magnetite >Scheelite <Pyrite <Arsenopyrite Euhedral Platelets / masses of interpenetrating Laths Cleavage / Twinning common Arsenopyrite Bismuth Bismuthinite Cassiterite Chalcopyrite Gold Molybdenite Scheelite Common / Deep Red, especially in oil Low 15% Soft (319-390) Monoclinic Wolframite is technically not a mineral name. It ought to be referred to as the Ferberite-Hübnerite Series
Zincite ZnO Pinkish Brown None / Masked by internal reflections Masked by internal reflections <Franklinite <Hausmannite Anhedral grains Cleavage may be visible / Forms oriented intergrowths with Hausmannite Franklinite Hausmannite Common / Red to Yellowish Low 11% Soft (205-221) Hexagonal