Classification of Minerals

Classification of Minerals

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):

  1. Talc
  2. Gypsum
  3. Calcite
  4. Fluorite
  5. Apatite
  6. Orthoclase
  7. Quartz
  8. Topaz
  9. Corundum
  10. 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.

minerals

minerals_and_their_characteristicscharacteristics_of_mineralsManganiteMarbleMarcasite Marmatite Melaconite Melilite Mercury Metacinnabarite Millerite Mimetite Molybdenite Molybdite Monazite Mottramite Muscovite Naumannite Nephelite Niccolite Nitre Olivine Opal Orpiment Orthoclase Pentlandite Petzite Phosphate_Rock Platinum Polianite Polybasite Powellite Proustite Psilomelane Pyrargyrite Pyrite Pyrolusite Pyromorphite Pyrope Pyrophyllite Quartz Realgar Rhodochrosite Rhodonite Roscoelite Ruby Rutile Scheelite Senarmontite Serpentine Siderite Silver Smaltite Smithsonite Soda_Nitre Sperrylite Spessartite Sphalerite Spinel Spodumene Stannite Stephanite Stibnite Strontianite Sulfur Sylvanite Sylvite Talc Tantalite Tennantite Tenorite TetraDymite Tetrahedrite Titanite Topaz Tourmaline Tremolite Triphylite Ullmannite Uraninite Uvarovite Valentinite Vermiculite Willemite Witherite Wolframite Wulfenite Zaratite Zincite Zircon Actinolite Albite Almandite Altaite Alunite Amosite Analcite Andalusite Andradite Anglesite Anorthite Anthophyllite Apatite Aragonite Argentite Argyrodite Arsenopyrite Atacamite Azurite Barite Bauxite Bentonite Beryl Beryllonite Biotite Bismite Bismuth Bismuthinite Bismutite Borax Bornite Bournonite Braunite Breithauptite Brochantite Brucite Calamine Calaverite Calcite Calomel Carnallite Carontite Cassiterite Celestite Cerargyrite Cerussite Cervantite Chalcanthite Chalcedony Chalcocite Chalcomentite Chalcopyrite Chert Chloanthite Chromite Chrysoberyl Chrysocolla Chrysolite Chrysotile Cinnabar Clausthalite Cobaltite Colemanite Columbite Copper Corundum Cosalite Crocoite Cryolite Cuprite Cyanite Descloizite Diamond Diaspore Diatomaceous_Earth Dolomite Enargite Epidote Epsom_Salt Erythrite Ferberite Fluorite Frankeinite Galena Garnet Garnierite Genthite Gibbsite Gold Graphite Greenockite Grossularite Gypsum Halite Halloysite Hausmannite Hematite Hessite Horneblende Huebnerite Hydrozincite Hypersthene Ilmenite Iodyrite Iridium Iridosmene Jamesonite Jefferisite Kainite Kaloinite Kermesite Kieserite Lepidolite Leucite Limestones Limonite Linnaeite Livingstonite Magnesite Magnetite

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 2Sb2O4 Sb2O3. 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 2Sb2O4 Sb2O3. 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.