DESCRIPTIVE MINERAL TABLE

DESCRIPTIVE MINERAL TABLE

I. Minerals with Metallic Luster

*Name and Composition*	*Hardness*	*Color*	*Streak*	*Conspicuous Features*
Graphite C Elemental carbon	1	Silvery gray to black	Dark gray to black	Greasy feel; Marks paper like a pencil; light weight; Forms flakes which demonstrate perfect basal cleavage; May also occur as short hexagonal prisms, or earthy masses with metallic, dull or earthy luster. Specific Gravity (S.G.) = 2.1-2.3
Galena PbS Lead sulfide	2 1/2	Silvery gray	Gray to black	Cubic or octahedral crystals, bright metallic luster, heavy. Tarnishes dull gray. Cubic cleavage. Breaks easily into tiny cubes. S.G. = 7.6.
Copper Cu Native Copper	2 ½ - 3	Copper-rose	Copper-rose	Copper-rose color on fresh surfaces. Tarnishes brown to green. Malleable. May form distorted cubes, octahedrons, and dendritic (root-like) masses. Rare crystals; usually in compact masses. Often has a pale green surface coating of malachite. S.G. = 8.8-8.9.
Gold Au Native Gold	2 ½ - 3	Gold, white-gold, rose-gold	Same as color	Color varies with impurities. Extremely heavy. May be extended or shaped by hammering or rolling (malleable). Dissolves only in aqua regia. Rare small crystals, and dendrites (tree-like growths); nuggets in sedimentary deposits.
Silver Ag Native Silver	2 ½ - 3	Silver-white	Silver-white	Usually tarnished dark gray. Irregular fracture. Very heavy. May be gouged or sliced with a knife (sectile). May occur as dendrites (see Gold) and wires in calcite and other minerals.
Bornite Cu₅FeS₄ Copper iron sulfide	3	Silvery blue, rose to red, or brown	Dark gray-black	"Peacock ore." Opaque. Tarnishes iridescent purple and blue; alteration coating common; brittle masses; conchoidal fracture possible. Cleavage poor to absent.
Chalcopyrite CuFeS₂ Copper iron sulfide	3 ½ - 4	Dark brass- yellow or golden	Dark gray to greenish-black	Often tarnished brown, greenish-black, red, or iridescent blue. Brittle, fairly soft, usually massive. Conchoidal fracture possible. Cleavage poor to absent. S.G. = 4.1-4.3.
Chromite FeCr₂O₄ Iron-chromium oxide	5.5-6	Silvery black to black	Dark brown	Tarnishes gray; Forms octahedra; Brittle; No cleavage; May be weakly magnetic: S.G. = 4.6-4.8.
Pyrite FeS₂ Iron sulfide	6 – 6.5	Light brass-yellow	Dark gray to black	"Fool’s Gold" much lighter than true gold. Opaque. Tarnishes brown; forms cubes, octahedra, or pyritohedra (5-sided face). Poor cleavage; fragile. S.G. = 5.0.
Magnetite Fe₃O₄ Iron Oxide	6	Silvery gray to black	Dark gray to black	Attracted to a magnet and can be magnetized. Opaque. Granular or octahedral crystals common. Tarnishes gray. No cleavage. S.G. = 5.2.
Hematite Fe₂O₃ Iron Oxide	6	Shiny steel gray May also be gray, black, or brick red.	Dark Red	Opaque. "Specular Hematite" has glittering silver flakes or wavy sheets. Tarnishes red; Streak is distincitive. Tendency to flake obscures true hardness. Hemitite with H>5 generally appears metallic; however, compare to information on soft Hematite in Table II. A.

II. Minerals with Non-Metallic Luster

A. Hardness <5.5

*Name and Composition*	*Hardness*	*Color*	*Luster*	*Conspicuous Features*
Talc Mg₃Si₄O₁₀(OH)₂ Hydrous rnagnesiurn silicate	1	White, gray, pale green or brown	Pearly or greasy	Extremely soft; soapy feel. Impurities may increase apparent hardness. Forms crypto-crystalline masses showing no cleavage, may have warped or perfect basal cleavage. Often in scaly masses. S.G. = 2.7-2.8.
Sulfur S Native Sulfur	1 ½ -2 ½	Yellow	Resinous, greasy	Yellow color with pale yellow streak, low hardness, light weight. Detectable sulfur odor. Forms transparent to translucent well-developed blocky crystals, as earthy masses, or as a fine coating on volcanic rock. S.G. = 2.1
Gypsum CaS0_{4 ·}2H₂O Hydrous calcium sulfate Selenite Satin Spar Alabaster	2	Colorless, white; or gray, sometimes pale orange or pink	Vitreous, pearly, silky or greasy	Selenite is clear, satin spar is fibrous, alabaster is massive. Selenite may occur in large (to 3 meter) sword-like crystals; or in bladed groups incorporating sand and known as desert roses." Selenite has one perfect cleavage with two additional weaker cleavage surfaces. Transparent to translucent. SG= 2.3
Chlorite Hydrous ferromagnesian aluminum silicate	2 – 2 ½	Dark green, in some cases light green.	Vitreous to earthy	Green color and micaceous habit (one good cleavage). Forms short prisms that split easily into thin flexible sheets (not elastic like mica). S.G. = 2-3.
Kaolinite Al ₂Si₄0₁₀(OH)₈ Hydrous aluminum silicate	2 – 2 ½	White, cream or very light brown.	Earthy, dull	Opaque; Usually in clay-like masses with dull appearance. Commonly forms earthy micro-crystalline masses; cleavage excellent but absent in hand samples. Soft, powdery texture, Smells earthy when damp. S.G. = 2.6
Cinnabar HgS Mercury sulfide	2 – 2 ½	Cinnamon red	Adamantine to dull	Color diagnostic. May appear almost metallic or in earthy, pinkish-red masses. Scarlet streak. Toxic.
Biotite Mica K(Mg, Fe)₃AISi₃O₁₀(OH)₂ Hydrous potassium aluminum ferromagnesian silicate	2 ½ - 3	Black, brown- black, or green- black	Pearly	Dark mica. Perfect basal cleavage. May occur in six-sided mica ‘books" and as scattered flakes. Forms very short prisms that split easily into very thin greenish-brown elastic sheets along one perfect cleavage. S.G. = 2.7-3.1.
Muscovite Mica KAl₂(Al Si₃O₁₀)(OH)₂ Hydrous potassium aluminum silicate	2 ½	Colorless, pale green, yellow,	Pearly	White mica. Perfect basal cleavage, Occurs in mica "books" and as scattered flakes. Forms short opaque prisms; peels into thin elastic transparent sheets along one perfect cleavage. S.G. = 2.7-3.0.
Lepidolite Mica KLi ₂(AISi₄O₁₀)(OH)₂ Hydrous potassium lithium aluminum silicate	2 ½ - 4	Colorless, lilac, yellow	Vitreous to pearly	Lilac color is diagnostic. Often in granular masses of small mica "books". Lavender mica.
Halite NaCI Sodium chloride	2½	Colorless, white, yellow, brown, blueish, grayish, salmon, or reddish	Vitreous to greasy	Transparent to translucent. Easily dissolves in water. Forms cubes; excellent cubic cleavage, often has stepped-down "hopper" faces. Crystal masses or coatings on other material. Brittle, S.G. = 2.1-2.6.
Chrysocolla CuSiO₄ · 2H₂O Hydrated copper silicate	2-4	Pale blue to blue-green	Earthy	Very light blue streak; Opaque; Forms amorphous crusts or may be massive; Conchoidal fracture; S.G. = 2.0-2.4.
Serpentine Mg₆Si₄O₁₀(OH)₈ Hydrous magnesian silicate	2-5	Pale or dark green, yellow, gray	Dull, silky or pearly	Forms dull or silky masses and asbestos forms; No cleavage; S.G. = 2.2-2.6.
Calcite CaCO₃ Calcium carbonate	3	Colorless, white, or yellow, but may be green, brown, blue, or pink.	Vitreous or pearly	Effervesces freely in cold dilute hydrochloric acid. Transparent to opaque; Excellent cleavage in three directions not at 90° , Forms prisms, rhombohedra. S.G. = 2.7.
Barite BaSO₄ Barium sulfate	3 –3 ½	Colorless to white, with tints of brown, yellow, blue, or red	Vitreous to pearly	Forms short tabular crystals or blade which in circular arrangement form "barite roses." Brittle; Cleavage may be good to excellent in two directions; Heavy. S.G.= 4.5.
Sphalerite ZnS Zinc sulfide	3 ½ - 4	Usually yellow-brown; also black, green, red	Adamantine to metallic	Pale yellow odorous (sulfur) streak in most color varieties. Occurs as crystals, compact masses, and coatings. Perfect cleavage (dodecahedral), or cleavage chunks may appear triangular in shape, rarely possible to count all cleavage directions. SG. 3.9-4.0.
Azurite Cu₃(CO₃)₂(OH)₂ Hydrous copper carbonate	3 ½ - 4	Azure blue	Dull	Light blue streak. Color is distinctive deep blue; Forms crusts of small crystals, opaque earthy or radiating masses, or short and long prisms; Brittle; Effervesces in dilute HCl. Frequently associated with malachite. S.G. = 3.7-3.8.
Malachite Cu₂C0₃(OH)₂ Hydrous copper carbonates	3 ½ - 4	Bright green, pale green, or gray green	Dull or velvety	Usually in crusts, frequently laminated exhibiting color banding in shades of green, masses, or microcrystals; Effeversces in dulute HCl; S.G. 3-9-4.0.
Dolomite CaMg(CO₃)₂ Calcium magnesium carbonate	3 ½ - 4	White, gray, cream, yellow, or pink	Vitreous to pearly	Usually opaque; Slowly effervesces in HCl when powdered (streak); Pale pink color is indicative. Often associated with and resembles calcite; perfect rhombohedral cleavage; S.G. = 2.8-2.9.
Fluorite CaF₂ Calcium fluoride	4	Colorless, all pastels, deep purple	Vitreous to pearly	Crystals often cubic or octahedral. Color banding common. Usually fluorescent in ultraviolet light. Octahedral cleavage.
Kyanite Al₂(SiO₄)O Aluminum silicate	4-7	Blue, pale green, white or gray	Pearly	Translucent to transparent; Forms blades, scratches glass parallel to blades, does not scratch glass perpendicular to blades; S.G. 3.6-3.7.
Apatite Ca₅F(P0₄)₃ Calcium/Fluorophosphates	5	Green, brown, blue, white, purple, or colorless	Vitreous to resinous	Transparent to opaque; Brittle; Conchoidal fracture; Forms hexagonal prisms. One poor cleavage may be visible. S.G. = 3.1-3.4.
Hematite Fe₂0₃ Iron oxide	5 or much less	Dull brownish red to bright red	Sub-metallic to earthy	Red-brown streak; Often earthy and too powdery for accurate hardness test; May be granular or oolitic; Crystals rare; no cleavage. With H<5 (soft) generally appears nonmetallic (earthy); however, compare to information on "hard" Hematite in Table I. S.G. = 2.1-2.6.
Goethite FeO(OH) Hydrous iron oxide	5 – 5 ½	Dark rusty brown, ochre yellow	Dull, earthy	Streak distinctive yellow-brown. Often spongy, porous or earthy; also bladed, fibrous, as layers of radiating microscopic crystals, or in cubes and pyritohedrons as an alteration of pyrite. S.G. = 4.3.

II. Minerals with Non-Metallic Luster

Hardness > 5.5

*Name and Composition*		*Hardness*	*Color*		*Luster*	*Conspicuous Features*
Rhodonite MnSiO₃ Manganese silicate		6	Pink to deep rose		Pearly	Massive, dense or granular aggregates often have black veins. Color and hardness diagnostic. Blocky crystals, nearly 90° cleavage.
Actinolite (Amphibole) Comples hydrous calcium ferroganmesian silicate		5 ½ - 6	White to light green		Vitreous, pearly or silky	Prismatic cleavage at 124° and 56° ; with subconchoidal to subeven fracture; froms slender, glassy, crystals.
Hornblende (Amphibole) calcium ferromagnesian aluminum silicate		5 ½ - 6 (barely scratches glass)	Greenish-black to black		Vitreous	White to light gray-green streak; Opaque; Usually massive; occasionally in chunky crystals, Forms prisms with two good cleavages at 124° and 56° ; Often splintery; S.G. = 3.0-3.3.
Augite (Pyroxene) calcium ferromagnesian silicate		6	Dark green to greenish black		Vitreous to dull	White to pale gray streak; Opaque, short 8-sided prisms; Usually duller and greener than closely related hornblende; Two good cleavages (87° and 93)° , and uneven fracture. S.G. = 3.2-3.5.
Potassium Feldspar KAlSi₃O₈ (Potassium Feldspar or K-spar) Potassium aluminum silicate Microcline Anorthite		6	White, pink, salmon, orange, brown, green		Pearly	Forms translucent prisms with subparallel exsolution lamellae (wavy internal pattern); pink color distinguishes it from plagioclase when present; Cleavage excellent in two directions at nearly 90° ; S.G. = 2.6-2.8.
Plagioclase Feldspar NaAISi₃O_8«CaAl₂Si₃O₈ Sodium and/or calcium aluminosilicate Albite Anorthite		6	Colorless, white, gray, or black.		Pearly	Translucent; May have iridescent play of colors from within; Forms striated (parallel grooved) tabular crystals or blades; Cleavage good in two directions at nearly 90° ; S.G. = 2.6-2.8.
Sillimanite Al₂(SiO₄)O Aluminum silicate		6-7	Pale brown, white or gray		Silky	One good cleavage plus fracture surfaces; forms slender prisms; S.G. = 3.2.
Olivine (Mg,Fe)₂SiO₄ Ferromagnesian silicate		6 ½ -7	Pale to dark olive green to yellow or brown		Vitreous to resinous	Forms short flat prisms, Crystals often appear as glassy green beads, isolated or in masses. Color distinctive. Conchoidal fracture possible; Cleavage absent; Brittle; S.G. = 3.3-3.4.
Epidote Ca₂(Al,Fe)₃Si₃O₁₂(OH) Complex aluminum silicate		6 ½ -7	Pale or dark green to yellow-green		Vitreous	Usually a dull avocado green when massive; crystals are shiny dark green, S.G. = 3.3-3.5.
Quartz Family (Si0₂) Silicon Dioxide Rock Crystal Milky Quartz Smoky Quartz Rose Quartz Amethyst Citrine Cryptocrystalline Varities Chalcedony Flint Chert Agate Jasper Opal (Si0₂) · nH₂O hydrated silicon dioxide		7 7 7 7 7 7 7 7 7 7 7 7 5 – 5 ½	Colorless/varies White Gray, brown Pink Purple Yellow Variable Gray-black White-gray Banded Red-brown or yellow Varies		Vitreous to greasy, waxy, etc. Waxy	Varieties occur in all colors; Transparent to translucent; Conchoidal fracture; No cleavage; Forms hexagonal prisms and pyramids, often with terminations and steps perpendicular to crystal length; S.G. = 2.7 Crystals may be in clusters, or line cavities in rock. Translucent to opaque. Massive, dense, often bumpy masses; waxy surface. Color banded or mottled appearance common. Not wholly crystalline. May line rock cavities to form geodes, or replace organic material to "petrify’ wood, shell or bone. Opaque, waxy luster S.G. = 2.5-2.8. Colorless to white, orange, yellow, brown, blue, gray, green, or red; May have play of colors (opalescence); amorphous; S.G. = 1.9-2.3.
Staurolite Iron magnesium zinc aluminum silicate		7 – 7 ½	Brown to gray-brown		Vitreous to dull	Tarnishes dull brown; Usually found as prismatic crystals, often twinned to form crosses; Crystal faces are pitted and rough. Cruciform twinning is diagnostic when present; Poor cleavage; S.G. = 3.7-3.8.
Tourmaline Complex borosilicate of aluminum, sodium, magnesium, iron, lithium		7 – 7 ½	Black, brown, green, pink, blue yellow		Vitreous	Typically elongated prismatic crystals with striated faces and triangular cross section. Common variety shiny black. Crystals often occur in parallel or radiating groups. No cleavage. S.G. = 3.0-3.2.
Garnet Fe₃AI₂(Si0₄) Iron aluminium silicate, with calcium and magnesium		7 – 7 ½	Usually red, black or brown also purple, green, yellow, pink		Vitreous to resinous	Commonly in shades of red "pidgeon’s blood red"; Dodecahedral crystals have diamond shaped faces. Color and hardness aid identification transparent to opaque. No cleavage; S.G. = 3.5-4.3.
Beryl Be₃AI₃ Si₆O₁₈ Beryllium aluminum silicate		7 ½-8	Colorless, white, pink, blue, light green, emerald green		Vitreous	Commonly pale green, and in 6-sided prisms with flat terminations. Harder than quartz. Pale blue variety is aquamarine; chromium green variety is emerald.
Topaz Al₂SiO₄(OH,F)₂ Hydrous fluoroaluminum silicate		8	Colorless, white, golden yellow, light blue		Vitreous	Internal rainbows. Striations on crystal faces. Distinct glassy prismatic crystals with perfect basal cleavage exhibiting diamond-shaped cross section.
Corundum Al₂0₃ Aluminum oxide		9	Gray, all pastels, red, dark blue, brown		Vitreous to greasy	Commonly in barrel-shaped hexagonal crystals, tapered or with striated flat ends. Extremely hard. No cleavage. S.G. = 3.9-4.1.
Diamond C Elemental carbon	10		Colorless, pastels, brown, blue, yellow, gray, black, red, green	Adamantine to greasy		Octahedral crystals with greasy luster. Hardest known substance. Two directions of cleavage.