Classification of Minerals

The first step in the identification of a mineral before any chemical tests are made should be the recognition of the physical and optical properties and occurrence of the mineral. The physical properties are discussed below.

Color: The color is fairly constant in some minerals but not in all, and commonly the color is due to pigments or impurities in the minerals.

Lustre: The lustre of a mineral is its appearance in ordinary reflected light. There are seven kinds of lustre: metallic, the lustre of metals; adamantine, that of uncut diamonds; vitreous, cut diamonds, or broken glass; resinous of the yellow resins; greasy; pearly; silky. There are five degrees of intensity of lustre recognized: splendent, shining, glistening, glimmering, dull.

Specific Gravity: An important factor in identifying a mineral is the specific gravity, or weight of the mineral in air compared with the weight of an equal volume of water. Minerals can be classed as heavy and light, thereby eliminating many of the possibilities that a specimen could be due to its other physical properties. Minerals with a specific gravity of 3.5 or more are generally considered as heavy, whereas minerals with a specific gravity of 3.2 or less are considered to be light.

Streak: The streak is more nearly constant than the color. The streak is determined by crushing the mineral, or by marking unglazed porcelain, or simply by scratching the mineral with a knife and observing the color of the powder. The color of the streak may differ considerably from the color of the mineral specimen as in the case of hematite, the streak which is always red although the color of this mineral may vary from red to black.

Hardness: The resistance to abrasion, or scratching. For convenience in description hardness is often designated by a number according to a scale devised by Mohs. This scale is as follows (talc being the softest and diamond the hardest):

Talc
Gypsum
Calcite
Fluorite
Apatite
Orthoclase
Quartz
Topaz
Corundum
Diamond

The approximate hardness can be easily determined by noting the ease or difficulty with which a mineral scratches or is scratched by one of the following:

Thumbnail……………………2.5
Quartz or flint ………………7.0
Copper or silver coin……. 3.0
Emery (wheel or paper)..8.0 to 9.0
Knife blade ………………….5.5 to 6.0
Corundum paper …………9.0
Window glass ……………….5.5 to 6.0
Carborundum ………………9.5
File ……………………………..6.5 to 7.0
Diamond ……………………..10.0

If you can scratch a mineral with a knife blade, but not with a copper or silver coin, its hardness lies between 3 and 6, etc.

Occurrence and Characteristics: Occurrence refers to the form in which it is found, other minerals with which it is associated in the deposit, and its relation to the enclosing rock. Occurrence is an extremely valuable factor in the identification of a mineral. Special Characteristics:

A) MAGNETISM: If a mineral is magnetic it may rapidly lead to the identification of the mineral. Magnetite, pyrrhotite, ilmenite, iron-platinum, and chromite may occur as a magnetic mineral.

B) SOLUBILITY: Minerals which are soluble in water may be one of the following: potash, soda, nitrates, borax, epsom salt, and halite.

C) TASTE: Soluble minerals usually have a characteristic taste.

Potash………………..Alkaline
Epsomite…………….Bitter-saline
Epsom Salt………….Bitter
Nitre…………………..Saline-cooling
Borax………………….Sweetish-alkaline
Sylvite…………………Bitter-saline
Carnalite……………..Bitter

D) ODOR: Some minerals emit characteristic odors. Examples:

Kaolinite, odor of clay, when breathed upon.
Arsenopyrite, odor of garlic upon heating.
Pyrite, sulfurous odor upon heating.

E) FEEL OR TOUCH: When a mineral is rubbed by the finger, it may have a characteristic feel. Examples:

Graphite feels greasy.
Kaolinite feels greasy.
Meerschaum feels smooth.
Molybdenite feels greasy.
Talc feels greasy.

In the following table, the figures after each name of an ore indicate the percentage of the element specified which the pure mineral contains. When this is variable or is merely mechanically included, an interrogation mark takes the place of the above-mentioned figure.

Important ores are in heavy face type, less common species are in lighter type, and minerals which are only occasionally mined and treated for the element specified are in italics. Each group is arranged in the order of decreasing importance.

Name	Formula	%Metal	Color	Lustre	Streak	Hardness	SG	Characteristics Occurrence
ACTINOLITE	Ca(MgFe)₃(SiO₃)₄	No metal source	Green	Vitreous		5.0-6.0	3.0-3.2	Usually long crystals, columnar or fibrous
ALBITE	NaAlSi₃Os	Al₂O₃-19.5%	White to blue	Vitreous	White	6.0-6.6	2.6-2.7	Occurs with gneiss, schists, pegmatite and limestone
ALMANDITE	Fe₃Al₂(SiO₄)₃	No metal source	Red to black			6.5-7.5	3.1-4.3	Accessory rock mineral; variety of garnet
ALTAITE	PbTe	61.9% Pb	Tin white Yellow tinge	Metallic	Grayish Black	3.0	8.2	Associated with pyrite, galena, tetrahedrite
ALUNITE	K₂(Al₂OH)_6. (SO₄)₄	K-9.4%. Al-19.6%	Pink-red	Vitreous Pearly	White	3.8	2.7	Associated with kaolin and pyrite
AMOSITE	(FeCaH₂Mn)OSiO₂	No metal source	Gray to green				2.2-2.3	Long fibered asbestos
ANALCITE	NaAlSi₂O₆. 2H₂O	Al₂O₃-23.2%	White	Vitreous	White	5.0-5.5	2.2-2.3	Common Zeolite; yields water
ANDALUSITE	Al₂SiO₅	Al₂O₃-63.2%	White Red-green	Vitreous		7.5	3.2	Nearly square prisms; occurs with gneiss, mica, schists
ANDRADITE	Ca₃Fe₂(SiO₄)₃	No metal source	Green Red-black	Adamantine		6.5-7.5	3.1-4.3	Garnet and sometimes used as a gem
ANGLESITE	PbSO₄	Pb-68.3%	Yellow Green-gray	Adamantine, Vitreous	White	2.8-3.0	6.1-6.4	Occurs in oxidation zones of lead veins
ANORTHITE	CaAl₂Si₂O₈	Al₂O₃-36.7%	White, Gray-red	Vitreous	White	6.0-6.5	2.7-2.8	Occurs in igneous rocks
ANTHOPHYLLITE	(MgFe)SiO₃	No metal source	Gray Brown-green	Vitreous	Uncolored, Grayish	5.0	3.2-3.2	Found in crystalline schists
APATITE	Ca₄(CaF) (PO₄)₃	P₂O₅-42.3%	Green-blue	Vitreous	White	4.5-5.0	3.2	Granular; frequently massive; common in metamorphic rocks
ARAGONITE	CaCO₃	CaO-56%	White	Vitreous	White	3.5-4.0	2.9	Found in beds of iron ore and gypsum
ARGENTITE	Ag₂S	Ag-87.1%	Black	Metallic	Shiny Black	2.0-2.5	7.2-7.4	Cuts like lead; with silver, cobalt and nickel
ARGYRODITE	3Ag₂S.GeS₂	Ag-73.5%	Steel gray red tinge	Metallic	Grayish Black	2.5	6.1	Occurs with sphalerite, siderite and marcasite
ARSENOPYRITE	FeAsS	Fe-34.3% As-46.0%	Steel Gray	Metallic	Gray, Black	5.5-6.0	5.9-6.3	Widely spread; yields sparks and garlic odor when struck
ATACAMITE	Cu₂(OH)₃Cl	Cu-59.5%	Green	Adamantine, Vitreous	Apple Green	3.0-3.5	3.8	Always of secondary origin with copper ores
AZURITE	2CuCo₃.Cu(OH)₂	Cu-55.0%	Blue	Vitreous, Dull	Blue	3.5-4.0	3.8-3.9	Occurs with other copper minerals
BARITE	BaSO4	BaO-65.7%	White, Blue-red	Vitreous	White	2.5-3.5	4.3-4.6	Found commonly as gangue of lead-zinc ores
BAUXITE	Al₂O₃.3H₂O	Al-34.9%	White-red Brown-yellow	Dull	Like Color	1.0-3.0	2.6	Chief ore of aluminum, occurs massive
BENTONITE	(CaMg)O, SiO₂(AlFe)₂O₃	No metal source	Blue			1.0	2.1	The clay of montmorillonite
BERYL	Be₃Al₂(SiO₃)₆	Be—5% Al₂O₃-19%	White, Green-blue	Vitreous	White	7.5-8.0	2.6-2.8	Often imbedded in quartz; with mica, feldspar
BERYLLONITE	NaBePO₄	Be-7.1%	White-yellow	Vitreous, Brilliant		5.8	2.8	Found with beryl, feldspar, columbite
BIOTITE	(HK)₂(MgFe)₂Al₂(SiO₄)₃	No metal source	Black-Brown	Pearly, Vitreous	White	2.5-3.0	2.7-3.1	Perfect cleavage into very thin leaves
BISMITE	Bi₂O₃	No metal source	Straw Yellow White	Pearly			4.4	Of secondary origin resulting from oxidation
BISMUTH	Bi	Bi-100%	Silver White	Metallic	Silver White	2.3	9.7	Native; with cobalt, nickel; brassy tarnish
BISMUTHINITE	Bi₂S₃	Bi-81.2%	Lead gray	Metallic	Like Color	2.0	6.4-6.5	Occurs in form of thin coating
BISMUTITE	(BiO)₂.CO₃.H₂O	No metal source	Green-white			4.0	6.9-7.7	Incrusting fibrous, or earthy and pulverulent
BORAX	Na₂B₄O₇.10 H₂O	B₂O₃-36.6% Na₂O-16.2%	White	Vitreous, Dull	White	2.0-2.5	1.7	Refer to introduction for characteristic taste
BORNITE	Cu₃FeS₄	Cu-63.3%	Reddish	Metallic	Blackish Gray	3.0-3.5	4.9-5.4	Associated with chalcocite; massive
BOURNONITE	3(PbCu₂)S.Sb₂S₃	Pb-24.7% Cu-42.5%	Steel gray Iron black	Metallic	Like Color	2.5-3.0	5.7-5.9	Occurs fine grained massive; brittle
BRAUNITE	3Mn₂O₃.MnSiO₃	Mn-78.3%	Steel gray Brownish black	Submetallic	Like Color	6.0-6.5	4.8	Occurs in porphyry; brittle
BREITHAUPTITE	NiSb	Ni-32.5% Sb-67.5%	Copper red	Metallic	Reddish Brown	5.5	7.5	Occurs with other sulfides and silver minerals
BROCHANTITE	CuSO₄.3Cu(OH)₂	Cu-56.2%	Green	Vitreous	Green	3.5-4.0	3.9	Found in oxidation zones of copper deposits
BRUCITE	MgO.H₂O	MgO-69%	White to gray blue, green	Pearly, Vitreous	White	2.5	2.4	Associated with serpentine; secondary mineral
CALAMINE	AuTe₂	Au-43.6%	Bronze yellow Silver-yellow tinge		Yellowish Gray	2.5	9.0	Similar to sylvanite, krennerite
CALAVERITE	CaCO₃	CaO-56%	Many colors	Vitreous	White	3.0	2.7	Transparent to opaque; many varieties
CALOMEL	HgCl	Hg-85% Cl-15%	White, yellow	Adamantine	Pale Yellow, White	1.0-2.0	6.5	Associated with cinnabar
CARNALLITE	KMgCl₃.6H₂O	K-14.1% Cl-38.3%	White	Shining		2.5	1.6	Strongly phosphorescent; taste-bitter
CARNOTITE	K₂O.2U₂O₃.V₂O₃.3H₂O Variable	Variable	Yellow	Vitreous, Dull	Yellow	1.5		Mixed with sands; yellow crystal line powder
CASSITERITE	SnO₂	Sn-78.8%	Brown,black, red	Adamantine	White, Light Brown	6.0-7.0	6.8-7.1	The source of tin; opaque to translucent
CELESTITE	SrSO₄	Sr-47.7%	Light blue, white, red	Vitreous	White	3.0-3.5	3.9-4.0	Often associated with sulphur; in beds of limestone
CERARGYRITE	AgCl	Ag-75.3%	Pearly gray	Waxy, greasy	White to Gray	1.0-1.5	5.6	Cuts like wax; exposure changes color to violet brown
CERUSSITE	PbCO₃	Pb-77.5%	White, gray	Adamantine	White	3.0-3.5	6.5-6.6	Specific gravity important; with lead ores
CERVANTITE	2Sb₂O₄Sb₂O₃. Sb₂O₃	Sb-79.4%	Yellow reddish white	Greasy, Pearly	White	4.0-5.0	4.1-5.3	Usually associated with stibnite
CHALCANTHITE	CuSO₄.5H₂O	CuO-31.8%	Blue	Vitreous	White	2.5	2.1-2.3	Formed by oxidation of copper sulphides
CHALCEDONY	SiO₂	No metal source	Pale blue, gray White to black	Waxy	White	7.0	2.6-2.7	Often contains some disseminated opal-silica
CHALCOCITE	Cu₂S	Cu-79.8%	Black-Gray	Metallic	Like Color	2.5-3.0	5.5-5.8	Highly polished surface where cut
CHALCOMENITE	CuSeO₃.2H₂O	Cu-28.1% Se-34.9%	Blue	Vitreous		2.5-3.0	3.8	With various selenides of silver copper, and lead
CHALCOPYRITE	CuFeS₂	Cu-34.6%	Brassy yellow	Metallic	Greenish Black	3.5-4.0	4.1-4.3	Softer than pyrite; with pyrite, galena, sphalerite
CHERT	SiO₂	No metal source	White-gray			7.0	2.6	Impure, coarse-grained, opaque flint
CHLOANTHITE	NiAs₂ Variable	NI-28.1% As-71.9%	Tin white, steel gray	Metallic	Grayish black	5.8	6.5	Associated with smaltite, cobalt, silver and copper
CHROMITE	FeO.Cr₂O₃	Cr-46.2%	Black	Vitreous	Dark Brown	5.5	4.3-4.6	Usually associated with serpentine; brittle
CHRYSOBERYL	BeOAl₂O₃	BeO-19.8%	Green	Vitreous	White	8.5	3.7-3.8	Resembling green glass; brittle
CHRYSOCOLLA	CuOSiO₂.2H₂O	Cu-36.2%	Blue, green	Vitreous, Dull	White	2.0-4.0	2.0-2.2	Adheres to dry tongue; important ore of copper
CHRYSOLITE	(MgFe)₂SiO₄	No metal source	Green	Vitreous	White or Yellowish	6.5-7.0	3.3	Occurs in granular masses; brittle
CHRYSOTILE	H₄Mg₃Si₂O₉		White, greenish	Metallic	White	1.7	2.2	Fibered asbestos; parallel fibers
CINNABAR	HgS	Hg-86.2%	Red	Adamantine, Submetallic	Scarlet	2.0-2.5	8.0-8.2	Only important ore of mercury; tastes “chalky”
CLAUSTHALITE	PbSe	Pb-72.4%	Lead gray	Metallic	Lead gray	2.8	8.0	Resembles granular galena
COBALTITE	CoAsS	Co-35.5%	Tin white, steel gray	Metallic	Grayish Black	5.5	6.0-6.3	Occurs commonly granular; ore of cobalt
COLEMANITE	Ca₂B₆O₁₁.5H₂O	No metal source	White, yellowish	Brilliant, Vitreous	White	4.0-4.5	2.4	Usually occurs as geodes; brittle
COLUMBITE	(FeMn)(CbTa)₂O₆	Variable-Ta₂O₅ 3.3 to 31.5%	Iron black	Submetallic	Dark Red, Black.	6.0	6.3	Brittle; nearly pure niobate
COPPER	Cu	Cu-100%	Copper red	Metallic	Copper red	2.8	8.8	Tarnishes easily; malleable
CORUNDUM	Al₂O₃	AI-52.9%	All colors	Vitreous, Adamantine	White	9.0	3.9-4.1	Brittle; very tough when compact
COSALITE	Pb₂Bi₂S₆	Pb-41.8% Bi-42.1%	Lead gray	Metallic	Black	2.8	6.5	In quartz veins; with pyrite, sphalerite
COVELLITE	CuS	Cu-66.5%	Blue	Submetallic	Black	1.5-2.0	4.6	Opaque, turns blue when moistened
CROCIDOLITE	NaFe(SiO₃)₂.FeSiO₃	No metal source	Blue to green	Silky, Dull	Like Color	4.0-5.0	3.2-3.3	Fibrous masses; like asbestos, valuable
CROCOITE	PbCrO₄	Pb-64.1% Cr-16.1%	Red	Adamantine	Orange Yellow	2.5	6.0	Found with quartz, galena, vanadinite
CRYOLITE	Na₃AlF₆	Al-13% F-54.4%	Snow white	Greasy to Vitreous	White	2.5	3.0	Appearance, hardness are distinctive
CUPRITE	Cu₂O	Cu-88.8%	Red	Adamantine to dull	Red	3.5-4.0	5.9-6.2	Brittle; transparent to opaque; fine grained
CYANITE	Al₂SiO₅	Al-33.3%	White, to blue or green	Vitreous, Pearly		5.0-7.0	3.6	Long, bladed triclinic crystals; sometimes fibrous
DESCLOIZITE	4RO.V₂O₅.H₂O	Variable. V₂O₅	Red, brown, black	Greasy	Orange	3.5	6.0	Associated with vanadinite
DIAMOND	C	C-100%	White, gray	Adamantine, Greasy	Ash Gray	10.0	3.5	Found with serpentine, placers, magnetite, gold
DIASPORE	Al₂O₃. H₂O	Al₂O₃-85%	Many colors	Vitreous	White	6.5-7.0	3.4	Occurs in thin scales; very brittle
DIATOMACEOUS EARTH	SiO₂.n H₂O		Yellow to brown	Vitreous	White to Gray	2.0	2.2	Siliceous; scratches glass; light In weight
DOLOMITE	CaMg (CO₃)₂	CaO-30.4% MgO-21.9%	White, gray, pink, yellow	Vitreous, Pearly	White	3.5-4.0	2.8-2.9	Effervesces vigorously with hydrochloric acid
ENARGITE	3CU₂S. AS₂S₅	Cu-48.4%	Iron black	Metallic	Black	3.0	4.4	Color and streak both black; prismatic cleavage
EPIDOTE	Ca₂(Al0H)(AlFe)₂ (SiO₄)₃	No metal source	Green	Vitreous, Dull	White	6.0-7.0	3.2-3.5	Brittle; usually granular
EPSOM SALT	MgSO₄.7 H₂O	Mg-9.9%	White	Vitreous	White	2.3	1.7	Tastes bitter and saline; in mineral waters
ERYTHRITE	CO₃AS₂O₈.8H₂O	Co-29.5%	Crimson, gray	Pearly	Paler than Color	1.5-2.5	3.0	Deposits of secondary origin; with cobalt ores
FERBERITE	FeWO₄	W-60.6%	Brown, black	Metallic		5.0-5.5	7.2-7.5	Found with other tungsten ores
FLUORITE	CaF₂	F-48.9%	All colors	Vitreous	White	4.0	3.0-3.3	Octahedral cleavage; brittle
FRANKEINITE	(ZnFeMn)O (FeMn)₂O₃	Zn-14.2% Mn-35.7%	Iron black	Metallic	Brown to Black	5.5-6.5	5.2	Usually associated with zincite; sometimes magnetic
GALENA	PbS	Pb-86.6%	Lead gray	Metallic	Lead Gray	3.0	7.4-7.6	Very brittle; cubic cleavage
GARNET	Various	No metal source	Red, brown, yellow	Vitreous	White	6.5-7.5	3.2-4.3	Usually imbedded in mica or other schists
GARNIERITE	H₂(NiMg)SiO₄	Ni-25% to 30%	Green	Dull, greasy	Greenish. White	2.0-4.0	2.4	Amorphous; source of nickel; with serpentine, chromite
GENTHITE	2NiO,2MgO. 3SiO₂.6 H₂O	Ni-22.6%	Green	Dull, greasy	Greenish. White	2.0-4.0	2.4	Similar to garnierite
GIBBSITE	Al(0H)₃	Al-34.6%	White, green	Pearly		2.0-3.5	2.4	Occurs under same conditions as bauxite
GOLD	Au	Au-100%	Golden	Metallic	Golden Yellow	2.8	15.6-19.3	Malleable; does not famish; many associations
GRAPHITE	C	C-100%	Black	Dull, Submetallic	Dark Gray, Iron Black	1.0-2.0	2.2	Soft; marks paper; feels greasy; often impure
GREENOCKITE	CdS	Cd-77.7%	Yellow	Adamantine	Yellow to red	3.0-3.5	5.0	Usually occurs as coating on zinc minerals
GROSSULARITE	Ca₃Al₂(SiO₄)₃	No metal source	White, green, yellow	Vitreous	White	6.5-7.5	3.4-3.7	Often imbedded in mica and schists; limestones
GYPSUM	CaSO₄.2H₂O	CaO-32.6%	White, red	Vitreous	White to Gray	1.5-2.0	2.3	In limestones, shales; monoclinic crystals
HALITE	NaCl	Na-39.4%	White	Vitreous	White	2.5	2.1-2.6	Taste-saline. Important source of sodium
HALLOYSITE	H₄Al₂O₃.2SiO₂.H₂O	No metal source	White, green, blue, red	Pearly, Waxy, dull		1.0-2.0	2.0-2.2	Often occurs in veins of ore as secondary product
HAUSMANNITE	Mn₃O₄	Mn-72%	Black,brown	Metallic	Brown	5.3	4.7	Associated with other manganese minerals
HEMATITE	Fe₂O₃	Fe-70%	Brown, red, black	Metallic, Dull Submetallic	Red, Brown	5.5-6.5	4.9-5.3	Becomes magnetic upon heating under reducing conditions
HESSITE	Ag₂Te	Ag-63%	Gray	Metallic	Black	2.5-3.0	8.3-8.9	With chalcopyrite, pyrite, and sphalerite
HORNEBLENDE	Variable	Variable	White, green, black	Vitreous		5.0-6.0	3.2	Many varieties; one of the amphiboles
HUEBNERITE	MnWO₄	Mn-18.1% W-60.7%	Brown	Submetallic	Yellowish Brown	5.0-5.5	7.2-7.5	Occurs with other tungsten minerals and galena
HYDROZINCITE	ZnCo₃.2Zn(OH)₂	Zn-59.5%	White, gray, yellow	Dull	White	2.0-2.5	3.6-3.8	Usually associated with other zinc ores
HYPERSTHENE	(FeMg)SiO₃	No metal source	Black	Pearly	Gray	5.0-6.0	3.5	Occurs in foliated or platy masses
ILMENITE	FeTiO₃	Ti-31.6%	Iron black	Metallic, Submetallic	Brown	5.0-6.0	4.5-5.0	Magnetic; with pyrite, horneblende, feldspars
IODYRITE	Agl	Ag-46%	Yellow, green			3.0-4.0	5.6-5.7	Usually in thin plates; rare
IRIDIUM	Variable	Variable	White	Metallic		6.7	22.7	With platinum and allied metals
IRIDOSMENE	IrOs(RhPtRu	Alloy-100%	Tin White	Metallic		6.0-7.0	19.3-21.1	Rare metals alloy
JAMESONITE	2PbS.Sb₂S₃	Pb-50.8% Sb-29.5%	Gray	Metallic	Grayish Black	2.0-3.0	5.5-6.0	Usually associated with quartz; brittle
JEFFERISITE	Variable	Variable.	Yellowish brown	Pearly	White	1.5	2.3	Mica loosely combined with water; with serpentine
KAINITE	MgSO₄.KCl.3H₂O	KCl-30.0%	White to red	Vitreous		2.8	2.1	Found in granular masses; with halite, sylvite
KAOLINITE	H₄Al₂Si₂O₉	Al₂O₃-39.5%	White, yellow	Pearly	Same as Color	2.0-2.5	2.6	Widespread; earthy odor; clay
KERMESITE	Sb₂S₂O	Sb-75.3%	Cherry	Adamantine, Metallic	Brownish Red	1.3	4.6	Occurs with stibnite
KIESERITE	MgSO₄.H₂O	Mg-17.6%	White, yellow	Vitreous		3.3	2.6	Often with gypsum and carnallite
LEPIDOLITE	KLi[Al(OHF)₂] Al(SiO₃)₃	Small amount of Li	Red, lilac, white	Pearly	White	3.0	2.8-3.3	Occurs in granite, gneiss; with muscovite
LEUCITE	KAI(SiO₃)₂	K₂O-21.5% Al₂O₃-23.5%	Gray	Vitreous, Dull	White	5.5-6.0	2.5	Occurs only in igneous rocks, particularly recent lava flows
LIMESTONES	Chiefly CaCO₃	Ca-40%	Variable	Dull	White	3.0	2.7	Widely distributed; large deposits
LIMONITE	2Fe₂O₃-3H₂O	Fe-59.9%	Brown, yellow	Submetallic	Yellowish Brown	5.0-5.5	3.6-4.0	Massive, fibrous or porous; magnetic after fusing
LINNAEITE	CO₃S₄	Co-58.0%	Steel gray	Metallic	Blackish Gray	5.5	4.8-5.0	Copper red tarnish; in gneiss with chalcopyrite
LIYINGSTONITE	HgS.2Sb₂S₃	Hg-22.0%	Lead gray	Metallic	Red	2	4.81	Resembles stibnite; fuses easily
MAGNESITE	MgCO₃	Mg-28.9%	White to black	Vitreous	White	4.0-4.5	3.1	Often associated with serpentine; chalk-like
MAGNETITE	FeO.Fe₂O₃	Fe-72.4%	Iron black	Metallic, Submetallic	Black	5.5-6.5	5.2	Strongly magnetic; many associations
MALACHITE	CuCO₃.Cu(OH)₂	Cu-57.5%	Green	Silky	Green	3.5-4.0	4.0	Usually associated with other copper minerals
MANGANITE	Mn₂O₃.H₂O	Mn-62.5%	Iron black, steel gray	Metallic, Submetallic	Brown	4.0	4.2-4.4	Hardness and streak are distinctive
MARBLE	Chiefly CaCO₃	Ca-40%	Variable	Vitreous, Earthy	White, Gray	3.0	2.7	Varieties based on accidental Impurities
MARCASITE	FeS₂	Fe-46.6%	Yellow	Metallic	Grayish, Brown, black	6.0-6.5	4.9	Same uses as pyrite; brittle
MARMATITE	(ZnFe)S Variable	Zn-46.5% to 56.9%	Yellow, brown, black	Adamantine	Brownish	5.0	3.9-4.2	Closely allied with galena; common zinc ore
MEUCONITE	CuO	Cu-79.9%	Black	Earthy, Metallic.		3.0-4.0	6.5	Sublimation product in volcanic regions
MELILITE	Ca₁₂Al₄Si₉O₃₆		White, yellow, green, brown	Vitreous		5	2.9-3.1	Formed from magmas; common in Portland cement
MERCURY	Hg	Hg-100%	Tin white	Metallic			13.59	Liquid; rarely found in metallic state
METACINNABARITE	HgS	Hg-86.2%	Grayish black	Metallic	Black	3	7.7	Found in upper portions of mercury deposits
MILLERITE	NiS	Ni-64.8%	Yellow	Metallic	Greenish Black	3.0-3.5	5.3-5.7	Valuable ore of nickel; needle like crystals
MIMETITE	(PbCl)Pb₄AS₃O₁₂	Pb-69.7%	Yellow to brown	Resinous	White	3.5	7.0-7.3	A minor ore of lead; uncommon species
MOLYBDENITE	MoS₂	Mo-60%	Lead gray	Metallic	Greenish Gray	1.0-1.5	4.7-4.8	Greasy; makes dark greenish mark on glazed paper
MOLYBDITE	MoO₃	Mo-66.67%	Yellow	Adamantine, Pearly		1.5	4.5	Occurs with molybdenite
MONAZITE	(CeLaDy)PO₄.ThSiO₄	ThO₂-9%	Yellow, brown	Resinous	White	5.0-5.5	4.9-5.3	Rounded grains; with gold, chromite, iron
MOTTRAMITE	Variable	Variable	Black, yellow	Resinous	Yellow	3	5.8	A vanadate of lead and copper
MUSCOVITE	H₂KAl₃(SiO₄)₂	Variable	Yellowish white	Vitreous, Pearly	White	2.0-2.5	2.8-3.0	Perfect cleavage into very thin leaves
NAUMANNITE	(Ag₂Pb)Se	Ag-43.0%	Iron black	Metallic	Iron Black	2.5	8	Malleable; in cubic crystals; selenide of silver and lead
NEPHELITE	NaAlSiO₄	No metal source	White, yellow	Vitreous, Greasy	White	5.5-6.0	2.5-2.7	Widely distributed in igneous rocks; usually massive
NICCOLITE	NiAs	Ni-44.1% As-55.9%	Copper red	Metallic	Brownish Black	5.0-5.5	7.3-7.7	Often found with a green coating; brittle; compact
NITRE	KNO₃	K-38.6% N-13.9%	White	Vitreous	White	2	2.1	Tastes saline and cooling; salt petre
OLIVINE	(MgFe)₂.SiO₄	No metal source	Green	Vitreous	White or Yellowish	6.5-7.0	3.3	Occurs in granular masses; brittle
OPAL	SiO₂.nH₂O	No metal source	All colors	Greasy, Vitreous	White	5.5-6.5	1.9-2.3	Amorphous silica; very smooth
ORPIMENT	AS₂S₃	As-61%	Lemon yellow	Resinous	Lemon Yellow	1.5-2.0	3.5	Usually associated with realgar; seldom valuable
ORTHOCLASE	KAlSi₃O₈	Al₂O₃-18.4%	Red, gray, yellow, white	Vitreous, Dull	White	6.0-6.5	2.5-2.6	Common constituent of igneous rocks; most common of all silicates
PENTLANDITE	(FeNi)S	Fe-42.0% Ni-22.0%	Yellow-bronze	Metallic	Black	3.5-4.0	4.6-5.0	Associated with pyrrhotite, millerite, chalcopyrite, etc.
PETZITE	(AuAg)₂ Te	Au-25.5% Ag-42%	Gray to black	Metallic	Gray	2.5	9.1	A rare but valuable ore of gold and silver; often tarnishes
PHOSPHATE ROCK	Ca₃(PO₄)₂	P₂O₅-32.1%	Gray	Dull	Gray	5	3.2	Occurs in massive deposits
PLATINUM	Pt	Pt-100%	Tin white, steel white	Metallic	Shiny Gray	4.5	17.0	Sometimes magnetic; with gold and chromite
POLIANITE	MnO₂	Mn-63.2%	Steel gray, iron gray	Metallic	Black	6.3	4.9	Looks like pyrolusite, but harder and dryer; rare
POLYBASITE	9Ag₂S.Sb₂S₃	Ag-75.6% Sb-9.4%	Iron black	Metallic	Black	2.0-3.0	6.0-6.2	With chalcopyrite, calcite, pyrargyrite, stephanite
POWELLITE	Ca(Mo,W)O₄	Variable	Greenish yellow	Resinous		3.5	4.5	Often associated with scheelite
PROUSTITE	3Ag₂S.As₂S₃	Ag-65.5%	Scarlet	Adamantine, Dull	Scarlet	2.0-2.5	5.6	Usually associated with other silver ores
PSILOMELANE	MnO₂.H₂O.K₂.BaO₂		Black	Submetallic Dull	Black, Brownish Black	5.0-6.0	3.7-4.7	Hardness and appearance distinctive; with pyrolusite
PYRARGYRITE	3Ag₂S.Sb₂S₃	Ag-60% Sb-22.2%	Black, reddish	Adamantine, Metallic	Purplish Red	2.5	5.8-5.9	Often associated with argentite and proustite
PYRITE	FeS₂	Fe-46.7%	Brass yellow	Metallic	Greenish Brn.-Blk.	6.0-6.5	5.0	In all types of rock; used in manufacture of H₂SO₄
PYROLUSITE	MnO₂	Mn-63.2%	Black, dark gray	Metallic, Dull	Black, Blu.-Blk	1.0-2.5	4.8	Soils fingers; hardness and streak are distinctive
PYROMORPHITE	Pb₃Cl(PO₄)₃	Pb-76.4%	Yellow	Greasy, Adamantine	White, Yel.-White	3.5-4.0	5.9-7.1	Alteration product of lead minerals
PYROPE	Mg₃Al₂(SiO₄)₃	No metal source	Red	Vitreous, Resinous		6.5-7.6	3.7	If transparent, then prized as a gem. Precious garnet.
PYROPHYLLITE	HAI(SiO₃)₂	Al₂O₃-28.3%	White, brown	Pearly, Dull	White	1.0-2.0	2.8-2.9	Feels greasy or soapy
PYROXENE	Ca(AlMgMnFe) (SiO₃)₂	No metal source	Green	Vitreous, Dull	White to Green	5.0-6.0	3.3	Commonly in igneous rocks; particularly volcanic
PYRRHOTITE	Fe₅S₆ to Fe₁₆S₁₇	Fe-61.5% Variable	Brownish yellow	Metallic	Grayish Black	3.5-4.6	4.6	Only magnetic sulphide and therefore distinctive
QUARTZ	SiO₂	Si-46.9%	Colorless, all colors	Vitreous	White	7.0	2.65-2.66	Different colors and varieties due to impurities
REALGAR	AsS	As-70.1%	Orange	Resinous	Orange	1.5-2.0	2.6	Usually associated with Orpiment; flexible
RHODOCHROSITE	MnCo₃	MnO-61.7%	Usually red	Vitreous, Pearly	White	3.5-4.5	3.5-3.6	Becomes darker upon exposure; an ore of manganese
RHODONITE	MnSiO₃	Mn-42.0%	Brownish red	Vitreous, Dull	White	5.5-6.5	3.4-3.7	With calcite, Zincite, tetrahedrite
ROSCOELITE	H₈K(MgFe)(AIV)₄ (SiO₃)₁₂	Variable	Brown	Pearly		Soft	2.9	Vanadium mica in which vanadium replaced aluminum
RUBY	Al₂O₃	Al-52.9%	Many colors	Adamantine, Vitreous		9.0	4.0	Brittle; when compact very tough; variety of corundum
RUTILE	TiO₂	Ti-60%	Brown, red, black	Adamantine, Submetallic	Light Brown	6.0-6.5	4.2	Frequently associated with iron
SCHEELITE	CaWO₄	W-63.9%	White-Yellowish	Vitreous, Adamantine	White	4.5-5.0	5.9-6.1	Brittle; important ore of tungsten
SENARMONTITE	Sb₂O₃	Sb-83.6%	Colorless, grayish	Vitreous, Dull		2	5.3	Formed by oxidation of stibnite
SERPENTINE	H₄Mg₃Si₂O₂	Mg-43%	Green, blackish or yellow, white	Wax-like, Silky	White	4.0	2.5-2.6	Feels smooth and sometimes slightly greasy
SIDERITE	FeCO₃	Fe-48.3%	Brown, gray	Vitreous, Pearly, Dull	White to Yellow	3.5-4.0	3.9	Magnetic upon heating; an ore of iron
SILVER	Ag	Ag-100%	Silver white	Metallic	Silver- White	2.8	10.5	Tarnishes easily; with gold, copper. etc.
SMALTITE	CoAS₂	Co-28.2%. As-71.8%	Tin white, steel gray	Metallic	Grayish Black	5.5-6.0	5.7-6.8	Occurs usually in veins with cobalt-nickel ores
SMITHSONITE	ZnO.CO₂	Zn-52%	Green, gray, blue	Vitreous, Dull	White, grayish	5.0	4.3-4.5	With sphalerite and calamine
SODA NITRE	NaNO₃		White, reddish brown; colorless	Vitreous	White	1.8	2.3	Taste-cooling; incrustations in beds; massive
SPERRYLITE	PtAS₂	Pt-56.6% As-43.4%	Tin white	Metallic, Brilliant	Black	6.5	10.6	Found with gold-quartz, covellite, limonite
SPESSARTITE	Mn₃Al₂(SiO₄)₃	No metal source	Purplish, red	Vitreous		3.5-4.0	3.9-4.1	Often associated with galena, chalcopyrite
SPHALERITE	ZnS	Zn-67.1%	Brown, yellow, reddish	Submetallic, Resinous	Light Brown, Yellow	8.0	3.5-4.1	Occurs in igneous rocks; often contact mineral
SPINEL	MgOAl₂O₃	Al₂O₃-71.8% MgO-28.2%	Yellowish, gray, brown.	Vitreous, Dull	White to Gray	6.5-7.0	3.1-3.2	Occurs in granite rocks; with lepidolite
SPODUMENE	LiAl(SiO₃)₂	Al₂O₃-27.4% Li₂O-8.4%	White, grayish	Vitreous, Dull	White	4.0	4.5	Has appearance of bronze
STANNITE	Cu₂S.FeS.SnS₂	Sn-27.5% Cu-29.5%	Steel gray, iron black	Metallic	Blackish	2.0-2.5	6.2-6.3	Associated with other silver ores
STEPHANITE	5Ag₂S.Sb₂S₃	Ag-68.5%	Iron black	Metallic	Iron Black	2.0-2.5	6.2-6.3	Associated with other silver ores
STIBNITE	Sb₂S₃	Sb-71.8%	Lead gray	Metallic	Lead Gray, Black	2.0	4.5-4.6	Tarnishes black; with gold-quartz, galena
STRONTIANITE	SrCO₃	Sr-59.3%	Yellow to brown Green	Vitreous, Greasy	White to. Gray	3.5-4.0	3.7	Like aragonite in structure; in dependent beds
SULFUR	S	S-100%	Yellow	Greasy, Adamantine	Pale Yellow	2.0	2.0	With celestite, clay, aragonite, gypsum
SYLVANITE	(AuAg)Te₂	Au-24.5% Ag-13.4%	White to steel gray	Metallic	Same as Color	1.5-2.0	7.9-8.3	Telluride of gold and silver
SYLVITE	KCl	K-52.4%	White, yellowish red	Vitreous	White	2.0	1.98	Taste-saline; soluble; bitter
TALC	H₂Mg₃(SiO₃)₄	Mg-19.2% Si-29.6%	Green to white	Pearly	White	1.0-1.5	2.7-2.8	Common; feels greasy; extensive beds
TANTALITE	FeTa₂O₆	Variable Ta₂O₆-65.6%	Iron black	Submetallic, Greasy, Dull	Reddish Brown	6.3	5.3-7.3	Iron and manganese content variable; with columbite
TENNANTITE	Cu₈As₂S₇ Variable	Cu-57.5% Variable	Steel gray, iron black	Metallic	Black, Reddish Brown	3.0-4.5	4.4-4.5	With chalcopyrite, sphalerite, galena, tetrahedrite
TENORITE	CuO	Cu-79.9%	Black	Metallic		3.0	5.8-6.3	Sublimation product in volcanic regions
TEPHROITE	Mn₂SiO₄	No metal source	Red, ash gray	Vitreous		6.5-7.0	4.0-4.1	Rarely in small crystals; like chrysolite
TETRADYMITE	Bi₂ (TeS)₃	Variable	Pale steel gray	Metallic		1.8	7.4	Soils paper; found in gold-quartz and igneous rocks
TETRAHEDRITE	4Cu₂S.Sb₂S₃	Cu-52.1% Sb-24.8%	Gray to black	Metallic	Black	3.0-4.5	4.4-5.1	Wide spread and varied occurrences
TITANITE	CaTiSiO₅	TiO₂-40.8%	Brown, gray, yellow, green	Adamantine	White	5.0-5.5	3.4-3.6	Usually confined to igneous rocks; accessory rock
Topaz	(AlF)₂SiO₄	No metal source	Many	Vitreous		8.0	3.4-3.6	Occurs in highly acid igneous rocks
TOURMALINE	[(NaLiK)₆(MgFe Ca)₃(AlCrFe)₂B₂SiO₅]	No metal source	Black, brown,& many others.	Vitreous to Resinous	White	7.0-7.5	3.0-3.2	Commonly found In granite, gneiss and pegmatite veins
TREMOLITE	CaMg₃(SiO₃)₄	No metal source	White to dark gray	Silky		5.0-6.0	2.9-3.4	Alters into actinolite
TRIPHYLITE	LiFePO₄	Li-4.4%	Greenish gray, bluish gray	Vitreous, Resinous		4.8	3.5	A phosphate of iron, manganese and lithium
ULLMANNITE	NiSbS	Ni-27.6% Sb-57.3%	Steel gray to white	Metallic	Grayish	5.3	6.4	With galena and chalcopyrite
URANINITE	UO₃,UO₂ Variable	Radium Source	Gray, green, brown	Submetallic to Greasy	Black, Gray, Green	5.5	9.0-9.7	Of primary and secondary origin; no definite formula
UVAROVITE	Ca₃Cr₂(SiO₄)₃	No metal source	Green	Vitreous		6.5-7.5	3.5	A form of garnet
VALENTINITE	Sb₂O₃	Sb-83.5%	White			2.5-3.0	5.6	Occurs as oxidation product of antimony
VANADINITE	(PbCl)Pb₄(VO₄)₃	Variable	Red, brown, yellow	Resinous	White or Yellow	2.7-3.0	6.6-7.1	Uncommon; found in altered lead deposits
VERMICULITE	3MgO.(FeAl)₂O₃ 3SiO₂	Variable	Grayish	Talc-like	Uncolored	1.5	2.7	Becomes worm-like threads upon heating-exfoliates
WILLEMITE	Zn₂SiO₄	Zn-58.5%	Green, yellow, brown	Vitreous, Dull	White or Grayish	5.5	3.9-4.2	Massive to granular; valuable zinc ore
WITHERITE	BaCO₃	BaO-77.7%	Yellow ,brown	Vitreous Pearly	White	3.4	4.4	Often fibrous; usually with galena
WOLFRAMITE	(FeMn)WO₄	W-51.3%	Gray, brown, black	Submetallic	Reddish- Brown	5.0-5.5	7.2-7.5	Differs from huebnerite in streak
WULFENITE	PbMoO₄	Pb-56.4% Mo-26.2%	Yellow, grayish	Resinous, Adamantine	White	3.0	6.8	Square, tubular crystals; often with beveled edges
ZARATITE	NiCO₃,2Ni(OH)2. 4H₂O	Ni-46.8%	Green			3	2.6	Emerald nickel; amorphous
ZINCITE	ZnO	Zn-80.3%	Red, yellow	Sub-Adamantine	Orange Yellow	4.0-4.5	5.4-5.7	Associated with other zinc ores
ZIRCON	ZrSiO₄	ZrO₂-67.2%	Yellow, gray	Adamantine	Colorless	7.5	4.2-4.7	In crystalline rocks; sometimes in iron ore beds

Name	Formula	Percent Metal	Color	Lustre	Streak	Hardness	Spec. Grav.	Characteristics—Occurrence
ACTINOLITE	Ca(MgFe)₃(SiO₃)₄	No metal source	Green	Vitreous		5.0-6.0	3.0-3.2	Usually long crystals, columnar or fibrous
ALBITE	NaAlSi₃Os	Al₂O₃-19.5%	White to blue	Vitreous	White	6.0-6.6	2.6-2.7	Occurs with gneiss, schists, pegmatite and limestone
ALMANDITE	Fe₃Al₂(SiO₄)₃	No metal source	Red to black			6.5-7.5	3.1-4.3	Accessory rock mineral; variety of garnet
ALTAITE	PbTe	61.9% Pb	Tin white Yellow tinge	Metallic	Grayish Black	3.0	8.2	Associated with pyrite, galena, tetrahedrite
ALUNITE	K₂(Al₂OH)_6. (SO₄)₄	K-9.4%. Al-19.6%	Pink-red	Vitreous Pearly	White	3.8	2.7	Associated with kaolin and pyrite
AMOSITE	(FeCaH₂Mn)OSiO₂	No metal source	Gray to green				2.2-2.3	Long fibered asbestos
ANALCITE	NaAlSi₂O₆. 2H₂O	Al₂O₃-23.2%	White	Vitreous	White	5.0-5.5	2.2-2.3	Common Zeolite; yields water
ANDALUSITE	Al₂SiO₅	Al₂O₃-63.2%	White Red-green	Vitreous		7.5	3.2	Nearly square prisms; occurs with gneiss, mica, schists
ANDRADITE	Ca₃Fe₂(SiO₄)₃	No metal source	Green Red-black	Adamantine		6.5-7.5	3.1-4.3	Garnet and sometimes used as a gem
ANGLESITE	PbSO₄	Pb-68.3%	Yellow Green-gray	Adamantine, Vitreous	White	2.8-3.0	6.1-6.4	Occurs in oxidation zones of lead veins
ANORTHITE	CaAl₂Si₂O₈	Al₂O₃-36.7%	White, Gray-red	Vitreous	White	6.0-6.5	2.7-2.8	Occurs in igneous rocks
ANTHOPHYLLITE	(MgFe)SiO₃	No metal source	Gray Brown-green	Vitreous	Uncolored, Grayish	5.0	3.2-3.2	Found in crystalline schists
APATITE	Ca₄(CaF) (PO₄)₃	P₂O₅-42.3%	Green-blue	Vitreous	White	4.5-5.0	3.2	Granular; frequently massive; common in metamorphic rocks
ARAGONITE	CaCO₃	CaO-56%	White	Vitreous	White	3.5-4.0	2.9	Found in beds of iron ore and gypsum
ARGENTITE	Ag₂S	Ag-87.1%	Black	Metallic	Shiny Black	2.0-2.5	7.2-7.4	Cuts like lead; with silver, cobalt and nickel
ARGYRODITE	3Ag₂S.GeS₂	Ag-73.5%	Steel gray red tinge	Metallic	Grayish Black	2.5	6.1	Occurs with sphalerite, siderite and marcasite
ARSENOPYRITE	FeAsS	Fe-34.3% As-46.0%	Steel Gray	Metallic	Gray, Black	5.5-6.0	5.9-6.3	Widely spread; yields sparks and garlic odor when struck
ATACAMITE	Cu₂(OH)₃Cl	Cu-59.5%	Green	Adamantine, Vitreous	Apple Green	3.0-3.5	3.8	Always of secondary origin with copper ores
AZURITE	2CuCo₃.Cu(OH)₂	Cu-55.0%	Blue	Vitreous, Dull	Blue	3.5-4.0	3.8-3.9	Occurs with other copper minerals
BARITE	BaSO4	BaO-65.7%	White, Blue-red	Vitreous	White	2.5-3.5	4.3-4.6	Found commonly as gangue of lead-zinc ores
BAUXITE	Al₂O₃.3H₂O	Al-34.9%	White-red Brown-yellow	Dull	Like Color	1.0-3.0	2.6	Chief ore of aluminum, occurs massive
BENTONITE	(CaMg)O, SiO₂(AlFe)₂O₃	No metal source	Blue			1.0	2.1	The clay of montmorillonite
BERYL	Be₃Al₂(SiO₃)₆	Be—5% Al₂O₃-19%	White, Green-blue	Vitreous	White	7.5-8.0	2.6-2.8	Often imbedded in quartz; with mica, feldspar
BERYLLONITE	NaBePO₄	Be-7.1%	White-yellow	Vitreous, Brilliant		5.8	2.8	Found with beryl, feldspar, columbite
BIOTITE	(HK)₂(MgFe)₂Al₂(SiO₄)₃	No metal source	Black-Brown	Pearly, Vitreous	White	2.5-3.0	2.7-3.1	Perfect cleavage into very thin leaves
BISMITE	Bi₂O₃	No metal source	Straw Yellow White	Pearly			4.4	Of secondary origin resulting from oxidation
BISMUTH	Bi	Bi-100%	Silver White	Metallic	Silver White	2.3	9.7	Native; with cobalt, nickel; brassy tarnish
BISMUTHINITE	Bi₂S₃	Bi-81.2%	Lead gray	Metallic	Like Color	2.0	6.4-6.5	Occurs in form of thin coating
BISMUTITE	(BiO)₂.CO₃.H₂O	No metal source	Green-white			4.0	6.9-7.7	Incrusting fibrous, or earthy and pulverulent
BORAX	Na₂B₄O₇.10 H₂O	B₂O₃-36.6% Na₂O-16.2%	White	Vitreous, Dull	White	2.0-2.5	1.7	Refer to introduction for characteristic taste
BORNITE	Cu₃FeS₄	Cu-63.3%	Reddish	Metallic	Blackish Gray	3.0-3.5	4.9-5.4	Associated with chalcocite; massive
BOURNONITE	3(PbCu₂)S.Sb₂S₃	Pb-24.7% Cu-42.5%	Steel gray Iron black	Metallic	Like Color	2.5-3.0	5.7-5.9	Occurs fine grained massive; brittle
BRAUNITE	3Mn₂O₃.MnSiO₃	Mn-78.3%	Steel gray Brownish black	Submetallic	Like Color	6.0-6.5	4.8	Occurs in porphyry; brittle
BREITHAUPTITE	NiSb	Ni-32.5% Sb-67.5%	Copper red	Metallic	Reddish Brown	5.5	7.5	Occurs with other sulfides and silver minerals
BROCHANTITE	CuSO₄.3Cu(OH)₂	Cu-56.2%	Green	Vitreous	Green	3.5-4.0	3.9	Found in oxidation zones of copper deposits
BRUCITE	MgO.H₂O	MgO-69%	White to gray blue, green	Pearly, Vitreous	White	2.5	2.4	Associated with serpentine; secondary mineral
CALAMINE	AuTe₂	Au-43.6%	Bronze yellow Silver-yellow tinge		Yellowish Gray	2.5	9.0	Similar to sylvanite, krennerite
CALAVERITE	CaCO₃	CaO-56%	Many colors	Vitreous	White	3.0	2.7	Transparent to opaque; many varieties
CALOMEL	HgCl	Hg-85% Cl-15%	White, yellow	Adamantine	Pale Yellow, White	1.0-2.0	6.5	Associated with cinnabar
CARNALLITE	KMgCl₃.6H₂O	K-14.1% Cl-38.3%	White	Shining		2.5	1.6	Strongly phosphorescent; taste-bitter
CARNOTITE	K₂O.2U₂O₃.V₂O₃.3H₂O Variable	Variable	Yellow	Vitreous, Dull	Yellow	1.5		Mixed with sands; yellow crystal line powder
CASSITERITE	SnO₂	Sn-78.8%	Brown,black, red	Adamantine	White, Light Brown	6.0-7.0	6.8-7.1	The source of tin; opaque to translucent
CELESTITE	SrSO₄	Sr-47.7%	Light blue, white, red	Vitreous	White	3.0-3.5	3.9-4.0	Often associated with sulphur; in beds of limestone
CERARGYRITE	AgCl	Ag-75.3%	Pearly gray	Waxy, greasy	White to Gray	1.0-1.5	5.6	Cuts like wax; exposure changes color to violet brown
CERUSSITE	PbCO₃	Pb-77.5%	White, gray	Adamantine	White	3.0-3.5	6.5-6.6	Specific gravity important; with lead ores
CERVANTITE	2Sb₂O₄Sb₂O₃. Sb₂O₃	Sb-79.4%	Yellow reddish white	Greasy, Pearly	White	4.0-5.0	4.1-5.3	Usually associated with stibnite
CHALCANTHITE	CuSO₄.5H₂O	CuO-31.8%	Blue	Vitreous	White	2.5	2.1-2.3	Formed by oxidation of copper sulphides
CHALCEDONY	SiO₂	No metal source	Pale blue, gray White to black	Waxy	White	7.0	2.6-2.7	Often contains some disseminated opal-silica
CHALCOCITE	Cu₂S	Cu-79.8%	Black-Gray	Metallic	Like Color	2.5-3.0	5.5-5.8	Highly polished surface where cut
CHALCOMENITE	CuSeO₃.2H₂O	Cu-28.1% Se-34.9%	Blue	Vitreous		2.5-3.0	3.8	With various selenides of silver copper, and lead
CHALCOPYRITE	CuFeS₂	Cu-34.6%	Brassy yellow	Metallic	Greenish Black	3.5-4.0	4.1-4.3	Softer than pyrite; with pyrite, galena, sphalerite
CHERT	SiO₂	No metal source	White-gray			7.0	2.6	Impure, coarse-grained, opaque flint
CHLOANTHITE	NiAs₂ Variable	NI-28.1% As-71.9%	Tin white, steel gray	Metallic	Grayish black	5.8	6.5	Associated with smaltite, cobalt, silver and copper
CHROMITE	FeO.Cr₂O₃	Cr-46.2%	Black	Vitreous	Dark Brown	5.5	4.3-4.6	Usually associated with serpentine; brittle
CHRYSOBERYL	BeOAl₂O₃	BeO-19.8%	Green	Vitreous	White	8.5	3.7-3.8	Resembling green glass; brittle
CHRYSOCOLLA	CuOSiO₂.2H₂O	Cu-36.2%	Blue, green	Vitreous, Dull	White	2.0-4.0	2.0-2.2	Adheres to dry tongue; important ore of copper
CHRYSOLITE	(MgFe)₂SiO₄	No metal source	Green	Vitreous	White or Yellowish	6.5-7.0	3.3	Occurs in granular masses; brittle
CHRYSOTILE	H₄Mg₃Si₂O₉		White, greenish	Metallic	White	1.7	2.2	Fibered asbestos; parallel fibers
CINNABAR	HgS	Hg-86.2%	Red	Adamantine, Submetallic	Scarlet	2.0-2.5	8.0-8.2	Only important ore of mercury; tastes “chalky”
CLAUSTHALITE	PbSe	Pb-72.4%	Lead gray	Metallic	Lead gray	2.8	8.0	Resembles granular galena
COBALTITE	CoAsS	Co-35.5%	Tin white, steel gray	Metallic	Grayish Black	5.5	6.0-6.3	Occurs commonly granular; ore of cobalt
COLEMANITE	Ca₂B₆O₁₁.5H₂O	No metal source	White, yellowish	Brilliant, Vitreous	White	4.0-4.5	2.4	Usually occurs as geodes; brittle
COLUMBITE	(FeMn)(CbTa)₂O₆	Variable-Ta₂O₅ 3.3 to 31.5%	Iron black	Submetallic	Dark Red, Black.	6.0	6.3	Brittle; nearly pure niobate
COPPER	Cu	Cu-100%	Copper red	Metallic	Copper red	2.8	8.8	Tarnishes easily; malleable
CORUNDUM	Al₂O₃	AI-52.9%	All colors	Vitreous, Adamantine	White	9.0	3.9-4.1	Brittle; very tough when compact
COSALITE	Pb₂Bi₂S₆	Pb-41.8% Bi-42.1%	Lead gray	Metallic	Black	2.8	6.5	In quartz veins; with pyrite, sphalerite
COVELLITE	CuS	Cu-66.5%	Blue	Submetallic	Black	1.5-2.0	4.6	Opaque, turns blue when moistened
CROCIDOLITE	NaFe(SiO₃)₂.FeSiO₃	No metal source	Blue to green	Silky, Dull	Like Color	4.0-5.0	3.2-3.3	Fibrous masses; like asbestos, valuable
CROCOITE	PbCrO₄	Pb-64.1% Cr-16.1%	Red	Adamantine	Orange Yellow	2.5	6.0	Found with quartz, galena, vanadinite
CRYOLITE	Na₃AlF₆	Al-13% F-54.4%	Snow white	Greasy to Vitreous	White	2.5	3.0	Appearance, hardness are distinctive
CUPRITE	Cu₂O	Cu-88.8%	Red	Adamantine to dull	Red	3.5-4.0	5.9-6.2	Brittle; transparent to opaque; fine grained
CYANITE	Al₂SiO₅	Al-33.3%	White, to blue or green	Vitreous, Pearly		5.0-7.0	3.6	Long, bladed triclinic crystals; sometimes fibrous
DESCLOIZITE	4RO.V₂O₅.H₂O	Variable. V₂O₅	Red, brown, black	Greasy	Orange	3.5	6.0	Associated with vanadinite
DIAMOND	C	C-100%	White, gray	Adamantine, Greasy	Ash Gray	10.0	3.5	Found with serpentine, placers, magnetite, gold
DIASPORE	Al₂O₃. H₂O	Al₂O₃-85%	Many colors	Vitreous	White	6.5-7.0	3.4	Occurs in thin scales; very brittle
DIATOMACEOUS EARTH	SiO₂.n H₂O		Yellow to brown	Vitreous	White to Gray	2.0	2.2	Siliceous; scratches glass; light In weight
DOLOMITE	CaMg (CO₃)₂	CaO-30.4% MgO-21.9%	White, gray, pink, yellow	Vitreous, Pearly	White	3.5-4.0	2.8-2.9	Effervesces vigorously with hydrochloric acid
ENARGITE	3CU₂S. AS₂S₅	Cu-48.4%	Iron black	Metallic	Black	3.0	4.4	Color and streak both black; prismatic cleavage
EPIDOTE	Ca₂(Al0H)(AlFe)₂ (SiO₄)₃	No metal source	Green	Vitreous, Dull	White	6.0-7.0	3.2-3.5	Brittle; usually granular
EPSOM SALT	MgSO₄.7 H₂O	Mg-9.9%	White	Vitreous	White	2.3	1.7	Tastes bitter and saline; in mineral waters
ERYTHRITE	CO₃AS₂O₈.8H₂O	Co-29.5%	Crimson, gray	Pearly	Paler than Color	1.5-2.5	3.0	Deposits of secondary origin; with cobalt ores
FERBERITE	FeWO₄	W-60.6%	Brown, black	Metallic		5.0-5.5	7.2-7.5	Found with other tungsten ores
FLUORITE	CaF₂	F-48.9%	All colors	Vitreous	White	4.0	3.0-3.3	Octahedral cleavage; brittle
FRANKEINITE	(ZnFeMn)O (FeMn)₂O₃	Zn-14.2% Mn-35.7%	Iron black	Metallic	Brown to Black	5.5-6.5	5.2	Usually associated with zincite; sometimes magnetic
GALENA	PbS	Pb-86.6%	Lead gray	Metallic	Lead Gray	3.0	7.4-7.6	Very brittle; cubic cleavage
GARNET	Various	No metal source	Red, brown, yellow	Vitreous	White	6.5-7.5	3.2-4.3	Usually imbedded in mica or other schists
GARNIERITE	H₂(NiMg)SiO₄	Ni-25% to 30%	Green	Dull, greasy	Greenish. White	2.0-4.0	2.4	Amorphous; source of nickel; with serpentine, chromite
GENTHITE	2NiO,2MgO. 3SiO₂.6 H₂O	Ni-22.6%	Green	Dull, greasy	Greenish. White	2.0-4.0	2.4	Similar to garnierite
GIBBSITE	Al(0H)₃	Al-34.6%	White, green	Pearly		2.0-3.5	2.4	Occurs under same conditions as bauxite
GOLD	Au	Au-100%	Golden	Metallic	Golden Yellow	2.8	15.6-19.3	Malleable; does not famish; many associations
GRAPHITE	C	C-100%	Black	Dull, Submetallic	Dark Gray, Iron Black	1.0-2.0	2.2	Soft; marks paper; feels greasy; often impure
GREENOCKITE	CdS	Cd-77.7%	Yellow	Adamantine	Yellow to red	3.0-3.5	5.0	Usually occurs as coating on zinc minerals
GROSSULARITE	Ca₃Al₂(SiO₄)₃	No metal source	White, green, yellow	Vitreous	White	6.5-7.5	3.4-3.7	Often imbedded in mica and schists; limestones
GYPSUM	CaSO₄.2H₂O	CaO-32.6%	White, red	Vitreous	White to Gray	1.5-2.0	2.3	In limestones, shales; monoclinic crystals
HALITE	NaCl	Na-39.4%	White	Vitreous	White	2.5	2.1-2.6	Taste-saline. Important source of sodium
HALLOYSITE	H₄Al₂O₃.2SiO₂.H₂O	No metal source	White, green, blue, red	Pearly, Waxy, dull		1.0-2.0	2.0-2.2	Often occurs in veins of ore as secondary product
HAUSMANNITE	Mn₃O₄	Mn-72%	Black,brown	Metallic	Brown	5.3	4.7	Associated with other manganese minerals
HEMATITE	Fe₂O₃	Fe-70%	Brown, red, black	Metallic, Dull Submetallic	Red, Brown	5.5-6.5	4.9-5.3	Becomes magnetic upon heating under reducing conditions
HESSITE	Ag₂Te	Ag-63%	Gray	Metallic	Black	2.5-3.0	8.3-8.9	With chalcopyrite, pyrite, and sphalerite
HORNEBLENDE	Variable	Variable	White, green, black	Vitreous		5.0-6.0	3.2	Many varieties; one of the amphiboles
HUEBNERITE	MnWO₄	Mn-18.1% W-60.7%	Brown	Submetallic	Yellowish Brown	5.0-5.5	7.2-7.5	Occurs with other tungsten minerals and galena
HYDROZINCITE	ZnCo₃.2Zn(OH)₂	Zn-59.5%	White, gray, yellow	Dull	White	2.0-2.5	3.6-3.8	Usually associated with other zinc ores
HYPERSTHENE	(FeMg)SiO₃	No metal source	Black	Pearly	Gray	5.0-6.0	3.5	Occurs in foliated or platy masses
ILMENITE	FeTiO₃	Ti-31.6%	Iron black	Metallic, Submetallic	Brown	5.0-6.0	4.5-5.0	Magnetic; with pyrite, horneblende, feldspars
IODYRITE	Agl	Ag-46%	Yellow, green			3.0-4.0	5.6-5.7	Usually in thin plates; rare
IRIDIUM	Variable	Variable	White	Metallic		6.7	22.7	With platinum and allied metals
IRIDOSMENE	IrOs(RhPtRu	Alloy-100%	Tin White	Metallic		6.0-7.0	19.3-21.1	Rare metals alloy
JAMESONITE	2PbS.Sb₂S₃	Pb-50.8% Sb-29.5%	Gray	Metallic	Grayish Black	2.0-3.0	5.5-6.0	Usually associated with quartz; brittle
JEFFERISITE	Variable	Variable.	Yellowish brown	Pearly	White	1.5	2.3	Mica loosely combined with water; with serpentine
KAINITE	MgSO₄.KCl.3H₂O	KCl-30.0%	White to red	Vitreous		2.8	2.1	Found in granular masses; with halite, sylvite
KAOLINITE	H₄Al₂Si₂O₉	Al₂O₃-39.5%	White, yellow	Pearly	Same as Color	2.0-2.5	2.6	Widespread; earthy odor; clay
KERMESITE	Sb₂S₂O	Sb-75.3%	Cherry	Adamantine, Metallic	Brownish Red	1.3	4.6	Occurs with stibnite
KIESERITE	MgSO₄.H₂O	Mg-17.6%	White, yellow	Vitreous		3.3	2.6	Often with gypsum and carnallite
LEPIDOLITE	KLi[Al(OHF)₂] Al(SiO₃)₃	Small amount of Li	Red, lilac, white	Pearly	White	3.0	2.8-3.3	Occurs in granite, gneiss; with muscovite
LEUCITE	KAI(SiO₃)₂	K₂O-21.5% Al₂O₃-23.5%	Gray	Vitreous, Dull	White	5.5-6.0	2.5	Occurs only in igneous rocks, particularly recent lava flows
LIMESTONES	Chiefly CaCO₃	Ca-40%	Variable	Dull	White	3.0	2.7	Widely distributed; large deposits
LIMONITE	2Fe₂O₃-3H₂O	Fe-59.9%	Brown, yellow	Submetallic	Yellowish Brown	5.0-5.5	3.6-4.0	Massive, fibrous or porous; magnetic after fusing
LINNAEITE	CO₃S₄	Co-58.0%	Steel gray	Metallic	Blackish Gray	5.5	4.8-5.0	Copper red tarnish; in gneiss with chalcopyrite
LIYINGSTONITE	HgS.2Sb₂S₃	Hg-22.0%	Lead gray	Metallic	Red	2	4.81	Resembles stibnite; fuses easily
MAGNESITE	MgCO₃	Mg-28.9%	White to black	Vitreous	White	4.0-4.5	3.1	Often associated with serpentine; chalk-like
MAGNETITE	FeO.Fe₂O₃	Fe-72.4%	Iron black	Metallic, Submetallic	Black	5.5-6.5	5.2	Strongly magnetic; many associations
MALACHITE	CuCO₃.Cu(OH)₂	Cu-57.5%	Green	Silky	Green	3.5-4.0	4.0	Usually associated with other copper minerals
MANGANITE	Mn₂O₃.H₂O	Mn-62.5%	Iron black, steel gray	Metallic, Submetallic	Brown	4.0	4.2-4.4	Hardness and streak are distinctive
MARBLE	Chiefly CaCO₃	Ca-40%	Variable	Vitreous, Earthy	White, Gray	3.0	2.7	Varieties based on accidental Impurities
MARCASITE	FeS₂	Fe-46.6%	Yellow	Metallic	Grayish, Brown, black	6.0-6.5	4.9	Same uses as pyrite; brittle
MARMATITE	(ZnFe)S Variable	Zn-46.5% to 56.9%	Yellow, brown, black	Adamantine	Brownish	5.0	3.9-4.2	Closely allied with galena; common zinc ore
MEUCONITE	CuO	Cu-79.9%	Black	Earthy, Metallic.		3.0-4.0	6.5	Sublimation product in volcanic regions
MELILITE	Ca₁₂Al₄Si₉O₃₆		White, yellow, green, brown	Vitreous		5	2.9-3.1	Formed from magmas; common in Portland cement
MERCURY	Hg	Hg-100%	Tin white	Metallic			13.59	Liquid; rarely found in metallic state
METACINNABARITE	HgS	Hg-86.2%	Grayish black	Metallic	Black	3	7.7	Found in upper portions of mercury deposits
MILLERITE	NiS	Ni-64.8%	Yellow	Metallic	Greenish Black	3.0-3.5	5.3-5.7	Valuable ore of nickel; needle like crystals
MIMETITE	(PbCl)Pb₄AS₃O₁₂	Pb-69.7%	Yellow to brown	Resinous	White	3.5	7.0-7.3	A minor ore of lead; uncommon species
MOLYBDENITE	MoS₂	Mo-60%	Lead gray	Metallic	Greenish Gray	1.0-1.5	4.7-4.8	Greasy; makes dark greenish mark on glazed paper
MOLYBDITE	MoO₃	Mo-66.67%	Yellow	Adamantine, Pearly		1.5	4.5	Occurs with molybdenite
MONAZITE	(CeLaDy)PO₄.ThSiO₄	ThO₂-9%	Yellow, brown	Resinous	White	5.0-5.5	4.9-5.3	Rounded grains; with gold, chromite, iron
MOTTRAMITE	Variable	Variable	Black, yellow	Resinous	Yellow	3	5.8	A vanadate of lead and copper
MUSCOVITE	H₂KAl₃(SiO₄)₂	Variable	Yellowish white	Vitreous, Pearly	White	2.0-2.5	2.8-3.0	Perfect cleavage into very thin leaves
NAUMANNITE	(Ag₂Pb)Se	Ag-43.0%	Iron black	Metallic	Iron Black	2.5	8	Malleable; in cubic crystals; selenide of silver and lead
NEPHELITE	NaAlSiO₄	No metal source	White, yellow	Vitreous, Greasy	White	5.5-6.0	2.5-2.7	Widely distributed in igneous rocks; usually massive
NICCOLITE	NiAs	Ni-44.1% As-55.9%	Copper red	Metallic	Brownish Black	5.0-5.5	7.3-7.7	Often found with a green coating; brittle; compact
NITRE	KNO₃	K-38.6% N-13.9%	White	Vitreous	White	2	2.1	Tastes saline and cooling; salt petre
OLIVINE	(MgFe)₂.SiO₄	No metal source	Green	Vitreous	White or Yellowish	6.5-7.0	3.3	Occurs in granular masses; brittle
OPAL	SiO₂.nH₂O	No metal source	All colors	Greasy, Vitreous	White	5.5-6.5	1.9-2.3	Amorphous silica; very smooth
ORPIMENT	AS₂S₃	As-61%	Lemon yellow	Resinous	Lemon Yellow	1.5-2.0	3.5	Usually associated with realgar; seldom valuable
ORTHOCLASE	KAlSi₃O₈	Al₂O₃-18.4%	Red, gray, yellow, white	Vitreous, Dull	White	6.0-6.5	2.5-2.6	Common constituent of igneous rocks; most common of all silicates
PENTLANDITE	(FeNi)S	Fe-42.0% Ni-22.0%	Yellow-bronze	Metallic	Black	3.5-4.0	4.6-5.0	Associated with pyrrhotite, millerite, chalcopyrite, etc.
PETZITE	(AuAg)₂ Te	Au-25.5% Ag-42%	Gray to black	Metallic	Gray	2.5	9.1	A rare but valuable ore of gold and silver; often tarnishes
PHOSPHATE ROCK	Ca₃(PO₄)₂	P₂O₅-32.1%	Gray	Dull	Gray	5	3.2	Occurs in massive deposits
PLATINUM	Pt	Pt-100%	Tin white, steel white	Metallic	Shiny Gray	4.5	17.0	Sometimes magnetic; with gold and chromite
POLIANITE	MnO₂	Mn-63.2%	Steel gray, iron gray	Metallic	Black	6.3	4.9	Looks like pyrolusite, but harder and dryer; rare
POLYBASITE	9Ag₂S.Sb₂S₃	Ag-75.6% Sb-9.4%	Iron black	Metallic	Black	2.0-3.0	6.0-6.2	With chalcopyrite, calcite, pyrargyrite, stephanite
POWELLITE	Ca(Mo,W)O₄	Variable	Greenish yellow	Resinous		3.5	4.5	Often associated with scheelite
PROUSTITE	3Ag₂S.As₂S₃	Ag-65.5%	Scarlet	Adamantine, Dull	Scarlet	2.0-2.5	5.6	Usually associated with other silver ores
PSILOMELANE	MnO₂.H₂O.K₂.BaO₂		Black	Submetallic Dull	Black, Brownish Black	5.0-6.0	3.7-4.7	Hardness and appearance distinctive; with pyrolusite
PYRARGYRITE	3Ag₂S.Sb₂S₃	Ag-60% Sb-22.2%	Black, reddish	Adamantine, Metallic	Purplish Red	2.5	5.8-5.9	Often associated with argentite and proustite
PYRITE	FeS₂	Fe-46.7%	Brass yellow	Metallic	Greenish Brn.-Blk.	6.0-6.5	5.0	In all types of rock; used in manufacture of H₂SO₄
PYROLUSITE	MnO₂	Mn-63.2%	Black, dark gray	Metallic, Dull	Black, Blu.-Blk	1.0-2.5	4.8	Soils fingers; hardness and streak are distinctive
PYROMORPHITE	Pb₃Cl(PO₄)₃	Pb-76.4%	Yellow	Greasy, Adamantine	White, Yel.-White	3.5-4.0	5.9-7.1	Alteration product of lead minerals
PYROPE	Mg₃Al₂(SiO₄)₃	No metal source	Red	Vitreous, Resinous		6.5-7.6	3.7	If transparent, then prized as a gem. Precious garnet.
PYROPHYLLITE	HAI(SiO₃)₂	Al₂O₃-28.3%	White, brown	Pearly, Dull	White	1.0-2.0	2.8-2.9	Feels greasy or soapy
PYROXENE	Ca(AlMgMnFe) (SiO₃)₂	No metal source	Green	Vitreous, Dull	White to Green	5.0-6.0	3.3	Commonly in igneous rocks; particularly volcanic
PYRRHOTITE	Fe₅S₆ to Fe₁₆S₁₇	Fe-61.5% Variable	Brownish yellow	Metallic	Grayish Black	3.5-4.6	4.6	Only magnetic sulphide and therefore distinctive
QUARTZ	SiO₂	Si-46.9%	Colorless, all colors	Vitreous	White	7.0	2.65-2.66	Different colors and varieties due to impurities
REALGAR	AsS	As-70.1%	Orange	Resinous	Orange	1.5-2.0	2.6	Usually associated with Orpiment; flexible
RHODOCHROSITE	MnCo₃	MnO-61.7%	Usually red	Vitreous, Pearly	White	3.5-4.5	3.5-3.6	Becomes darker upon exposure; an ore of manganese
RHODONITE	MnSiO₃	Mn-42.0%	Brownish red	Vitreous, Dull	White	5.5-6.5	3.4-3.7	With calcite, Zincite, tetrahedrite
ROSCOELITE	H₈K(MgFe)(AIV)₄ (SiO₃)₁₂	Variable	Brown	Pearly		Soft	2.9	Vanadium mica in which vanadium replaced aluminum
RUBY	Al₂O₃	Al-52.9%	Many colors	Adamantine, Vitreous		9.0	4.0	Brittle; when compact very tough; variety of corundum
RUTILE	TiO₂	Ti-60%	Brown, red, black	Adamantine, Submetallic	Light Brown	6.0-6.5	4.2	Frequently associated with iron
SCHEELITE	CaWO₄	W-63.9%	White-Yellowish	Vitreous, Adamantine	White	4.5-5.0	5.9-6.1	Brittle; important ore of tungsten
SENARMONTITE	Sb₂O₃	Sb-83.6%	Colorless, grayish	Vitreous, Dull		2	5.3	Formed by oxidation of stibnite
SERPENTINE	H₄Mg₃Si₂O₂	Mg-43%	Green, blackish or yellow, white	Wax-like, Silky	White	4.0	2.5-2.6	Feels smooth and sometimes slightly greasy
SIDERITE	FeCO₃	Fe-48.3%	Brown, gray	Vitreous, Pearly, Dull	White to Yellow	3.5-4.0	3.9	Magnetic upon heating; an ore of iron
SILVER	Ag	Ag-100%	Silver white	Metallic	Silver- White	2.8	10.5	Tarnishes easily; with gold, copper. etc.
SMALTITE	CoAS₂	Co-28.2%. As-71.8%	Tin white, steel gray	Metallic	Grayish Black	5.5-6.0	5.7-6.8	Occurs usually in veins with cobalt-nickel ores
SMITHSONITE	ZnO.CO₂	Zn-52%	Green, gray, blue	Vitreous, Dull	White, grayish	5.0	4.3-4.5	With sphalerite and calamine
SODA NITRE	NaNO₃		White, reddish brown; colorless	Vitreous	White	1.8	2.3	Taste-cooling; incrustations in beds; massive
SPERRYLITE	PtAS₂	Pt-56.6% As-43.4%	Tin white	Metallic, Brilliant	Black	6.5	10.6	Found with gold-quartz, covellite, limonite
SPESSARTITE	Mn₃Al₂(SiO₄)₃	No metal source	Purplish, red	Vitreous		3.5-4.0	3.9-4.1	Often associated with galena, chalcopyrite
SPHALERITE	ZnS	Zn-67.1%	Brown, yellow, reddish	Submetallic, Resinous	Light Brown, Yellow	8.0	3.5-4.1	Occurs in igneous rocks; often contact mineral
SPINEL	MgOAl₂O₃	Al₂O₃-71.8% MgO-28.2%	Yellowish, gray, brown.	Vitreous, Dull	White to Gray	6.5-7.0	3.1-3.2	Occurs in granite rocks; with lepidolite
SPODUMENE	LiAl(SiO₃)₂	Al₂O₃-27.4% Li₂O-8.4%	White, grayish	Vitreous, Dull	White	4.0	4.5	Has appearance of bronze
STANNITE	Cu₂S.FeS.SnS₂	Sn-27.5% Cu-29.5%	Steel gray, iron black	Metallic	Blackish	2.0-2.5	6.2-6.3	Associated with other silver ores
STEPHANITE	5Ag₂S.Sb₂S₃	Ag-68.5%	Iron black	Metallic	Iron Black	2.0-2.5	6.2-6.3	Associated with other silver ores
STIBNITE	Sb₂S₃	Sb-71.8%	Lead gray	Metallic	Lead Gray, Black	2.0	4.5-4.6	Tarnishes black; with gold-quartz, galena
STRONTIANITE	SrCO₃	Sr-59.3%	Yellow to brown Green	Vitreous, Greasy	White to. Gray	3.5-4.0	3.7	Like aragonite in structure; in dependent beds
SULFUR	S	S-100%	Yellow	Greasy, Adamantine	Pale Yellow	2.0	2.0	With celestite, clay, aragonite, gypsum
SYLVANITE	(AuAg)Te₂	Au-24.5% Ag-13.4%	White to steel gray	Metallic	Same as Color	1.5-2.0	7.9-8.3	Telluride of gold and silver
SYLVITE	KCl	K-52.4%	White, yellowish red	Vitreous	White	2.0	1.98	Taste-saline; soluble; bitter
TALC	H₂Mg₃(SiO₃)₄	Mg-19.2% Si-29.6%	Green to white	Pearly	White	1.0-1.5	2.7-2.8	Common; feels greasy; extensive beds
TANTALITE	FeTa₂O₆	Variable Ta₂O₆-65.6%	Iron black	Submetallic, Greasy, Dull	Reddish Brown	6.3	5.3-7.3	Iron and manganese content variable; with columbite
TENNANTITE	Cu₈As₂S₇ Variable	Cu-57.5% Variable	Steel gray, iron black	Metallic	Black, Reddish Brown	3.0-4.5	4.4-4.5	With chalcopyrite, sphalerite, galena, tetrahedrite
TENORITE	CuO	Cu-79.9%	Black	Metallic		3.0	5.8-6.3	Sublimation product in volcanic regions
TEPHROITE	Mn₂SiO₄	No metal source	Red, ash gray	Vitreous		6.5-7.0	4.0-4.1	Rarely in small crystals; like chrysolite
TETRADYMITE	Bi₂ (TeS)₃	Variable	Pale steel gray	Metallic		1.8	7.4	Soils paper; found in gold-quartz and igneous rocks
TETRAHEDRITE	4Cu₂S.Sb₂S₃	Cu-52.1% Sb-24.8%	Gray to black	Metallic	Black	3.0-4.5	4.4-5.1	Wide spread and varied occurrences
TITANITE	CaTiSiO₅	TiO₂-40.8%	Brown, gray, yellow, green	Adamantine	White	5.0-5.5	3.4-3.6	Usually confined to igneous rocks; accessory rock
Topaz	(AlF)₂SiO₄	No metal source	Many	Vitreous		8.0	3.4-3.6	Occurs in highly acid igneous rocks
TOURMALINE	[(NaLiK)₆(MgFe Ca)₃(AlCrFe)₂B₂SiO₅]	No metal source	Black, brown,& many others.	Vitreous to Resinous	White	7.0-7.5	3.0-3.2	Commonly found In granite, gneiss and pegmatite veins
TREMOLITE	CaMg₃(SiO₃)₄	No metal source	White to dark gray	Silky		5.0-6.0	2.9-3.4	Alters into actinolite
TRIPHYLITE	LiFePO₄	Li-4.4%	Greenish gray, bluish gray	Vitreous, Resinous		4.8	3.5	A phosphate of iron, manganese and lithium
ULLMANNITE	NiSbS	Ni-27.6% Sb-57.3%	Steel gray to white	Metallic	Grayish	5.3	6.4	With galena and chalcopyrite
URANINITE	UO₃,UO₂ Variable	Radium Source	Gray, green, brown	Submetallic to Greasy	Black, Gray, Green	5.5	9.0-9.7	Of primary and secondary origin; no definite formula
UVAROVITE	Ca₃Cr₂(SiO₄)₃	No metal source	Green	Vitreous		6.5-7.5	3.5	A form of garnet
VALENTINITE	Sb₂O₃	Sb-83.5%	White			2.5-3.0	5.6	Occurs as oxidation product of antimony
VANADINITE	(PbCl)Pb₄(VO₄)₃	Variable	Red, brown, yellow	Resinous	White or Yellow	2.7-3.0	6.6-7.1	Uncommon; found in altered lead deposits
VERMICULITE	3MgO.(FeAl)₂O₃ 3SiO₂	Variable	Grayish	Talc-like	Uncolored	1.5	2.7	Becomes worm-like threads upon heating-exfoliates
WILLEMITE	Zn₂SiO₄	Zn-58.5%	Green, yellow, brown	Vitreous, Dull	White or Grayish	5.5	3.9-4.2	Massive to granular; valuable zinc ore
WITHERITE	BaCO₃	BaO-77.7%	Yellow ,brown	Vitreous Pearly	White	3.4	4.4	Often fibrous; usually with galena
WOLFRAMITE	(FeMn)WO₄	W-51.3%	Gray, brown, black	Submetallic	Reddish- Brown	5.0-5.5	7.2-7.5	Differs from huebnerite in streak
WULFENITE	PbMoO₄	Pb-56.4% Mo-26.2%	Yellow, grayish	Resinous, Adamantine	White	3.0	6.8	Square, tubular crystals; often with beveled edges
ZARATITE	NiCO₃,2Ni(OH)2. 4H₂O	Ni-46.8%	Green			3	2.6	Emerald nickel; amorphous
ZINCITE	ZnO	Zn-80.3%	Red, yellow	Sub-Adamantine	Orange Yellow	4.0-4.5	5.4-5.7	Associated with other zinc ores
ZIRCON	ZrSiO₄	ZrO₂-67.2%	Yellow, gray	Adamantine	Colorless	7.5	4.2-4.7	In crystalline rocks; sometimes in iron ore beds

Source: This article is a reproduction of an excerpt of “In the Public Domain” documents held in 911Metallurgy Corp’s private library.