Mineral Identification

Graphite (C)

• Hardness: 1-2

• Color/Streak: Black / Black

• Luster: Metallic

• Cleavage: Perfect in one direction

• Habit: Foliated or scaly masses

• Distinguishing Features: Greasy feel, very soft, leaves marks on paper

• Uses: Lubricants, pencil “lead,” refractories

Diamond (C)

• Hardness: 10

• Color/Streak: Colorless / Clear to yellow

• Luster: Adamantine

• Cleavage: Perfect octahedral

• Habit: Octahedral or dodecahedral

• Distinguishing Features: Extremely hard, cold to the touch

• Uses: Gemstone, abrasive

Sulfur (S)

• Hardness: 1.5-2.5

• Color/Streak: Yellow / Yellow

• Luster: Resinous

• Cleavage: Conchoidal to uneven fracture

• Habit: Pyramidal, massive

• Distinguishing Features: Bright yellow color, smells like sulfur

• Uses: Sulfuric acid production, vulcanized rubber, insecticides

Copper (Cu)

• Hardness: 2.5-3

• Color/Streak: Copper-red / Copper

• Luster: Metallic

• Cleavage: Hackly fracture

• Habit: Dendritic, massive

• Distinguishing Features: Highly ductile, malleable, often has a green oxide coating

• Uses: Wiring, plumbing, industrial applications

Gold (Au)

• Hardness: 2.5-3

• Color/Streak: Yellow / Yellow

• Luster: Metallic

• Cleavage: Hackly fracture

• Habit: Octahedral, dendritic

• Distinguishing Features: Soft, malleable, very dense

• Uses: Jewelry, electronics

Pyrite (FeS₂)

• Hardness: 6-6.5

• Color/Streak: Pale brass yellow / Greenish black

• Luster: Metallic

• Cleavage: Conchoidal to uneven fracture

• Habit: Cubic, pyritohedral

• Distinguishing Features: "Fool’s Gold," cubic striated faces

• Uses: Associated with Au & Cu, sulfuric acid production

Chalcopyrite (CuFeS₂)

• Hardness: 3.5-4

• Color/Streak: Brass yellow / Greenish black

• Luster: Metallic

• Cleavage: Irregular, brittle

• Habit: Disphenoid

• Distinguishing Features: Often found with dolomite

• Uses: Copper ore

Galena (PbS)

• Hardness: 2.5

• Color/Streak: Lead-gray / Lead-gray

• Luster: Metallic

• Cleavage: Perfect cubic

• Habit: Cubic, penetration twins

• Distinguishing Features: Very heavy, cubic cleavage

• Uses: Lead ore, silver source

Sphalerite (ZnS)

• Hardness: 3.5-4

• Color/Streak: Pale yellow to dark brown / Yellow

• Luster: Resinous, submetallic

• Cleavage: Perfect dodecahedral (6 directions)

• Habit: Tetrahedral

• Distinguishing Features: Sulfur smell when streaked

• Uses: Zinc ore, also Cd, Ge & Ga source

Magnetite (Fe₃O₄)

• Hardness: 6

• Color/Streak: Black / Black

• Luster: Metallic

• Cleavage: Octahedral parting

• Habit: Octahedrons, massive

• Distinguishing Features: Strongly magnetic

• Uses: Iron ore

Hematite (Fe₂O₃)

• Hardness: 5.5-6.5

• Color/Streak: Red-brown to black / Red-brown

• Luster: Metallic to dull-earthy

• Cleavage: Parting on {10-11}

• Habit: Tabular, botryoidal

• Uses: Iron ore

Halite (NaCl)

• Hardness: 2.5

• Color/Streak: Colorless / White

• Luster: Transparent to translucent

• Cleavage: Perfect cubic

• Habit: Cubic, massive

• Distinguishing Features: Tastes like salt, dissolves in water

• Uses: Table salt, chemicals

Fluorite (CaF₂)

• Hardness: 4

• Color/Streak: Colorless, yellow, purple, green, blue / White

• Luster: Transparent

• Cleavage: Perfect octahedral

• Habit: Cubic, octahedral

• Distinguishing Features: Fluorescent under UV light

• Uses: Fluorine ore

Calcite (CaCO₃)

• Hardness: 3

• Color/Streak: White / White

• Luster: Vitreous to earthy

• Cleavage: Perfect rhombic

• Habit: Prismatic, rhombohedral

• Distinguishing Features: Effervesces in cold, dilute HCl

• Uses: Cement, lime, crushed stone

Dolomite (CaMg(CO₃)₂)

• Hardness: 3.5-4

• Color/Streak: White, pink / White

• Luster: Vitreous to pearly

• Cleavage: Perfect rhombic

• Habit: Saddle-shaped, rhombic

• Distinguishing Features: Soluble in cold HCl (does not effervesce)

• Uses: Building stone, crushed stone

Name: Pyrrhotite                                     Formula: FeS

Mineral Group: sulfide                                          Crystal Class: monoclinic

Hardness: 4                                                            Density: 4.6

Streak/Color: black-gray / brown-bronze

Luster: metallic

Cleavage/fracture: irregular

Habit: massive

Other: magnetic

Importance/Uses: associated Ni, Cu or Pt

Name: Chalcocite                                    Formula: Cu₂S

Mineral Group: sulfide                                          Crystal Class: monoclinic

Hardness: 2.5-3                                                      Density: 5.6

Streak/Color: gray-black / lead gray, tarnishes to black

Luster: metallic

Cleavage/fracture: one direction {110} poor, conchoidal

Habit: massive

Other: sectile, often in soft and sooty form

Importance/Uses: Cu-ore

Name: Bornite                                              Formula: Cu₅FeS₄

Mineral Group: sulfide                                          Crystal Class: orthorhombic

Hardness: 3                                                            Density: 5.07

Streak/Color: gray-black / bronze, tarnishes to purple-blue

Luster: metallic

Cleavage/fracture: irregular

Habit: massive

Other: "peacock ore"

Importance/Uses: Cu-ore

Name: Realgar                                             Formula: AsS

Mineral Group: sulfide                                          Crystal Class: monoclinic

Hardness: 1.5-2                                                      Density: 3.56

Streak/Color: red-orange / red-orange

Luster: resinous

Cleavage/fracture: {010} good

Habit: vertically striated prismatic

Other: sectile, always associated with orpiment

Importance/Uses: arsenic-ore, with Pb, Ag & Au

Name: Orpiment                                          Formula: As₂S₃

Mineral Group: sulfide                                          Crystal Class: monoclinic

Hardness: 1.5-2                                                      Density: 3.49

Streak/Color: pale yellow / lemon yellow

Luster: resinous

Cleavage/fracture: {010} perfect

Habit: tabular to short prismatic

Other: sectile, associated with realgar

Importance/Uses: arsenic-ore, with Pb, Ag & Au

Name: Cinnabar                                           Formula: HgS

Mineral Group: sulfide                                          Crystal Class: hexagonal

Hardness: 2-2.5                                                      Density: 8.18

Streak/Color: scarlet / vermilion-red

Luster: adamantine to metallic

Cleavage/fracture: {100} perfect

Habit: rhombohedral, penetrating twins

Other:

Importance/Uses: mercury-ore

Name: Limonite*                                         Formula: FeO(OH)

Mineral Group: hydroxide                                     Crystal Class: orthorhombic

Hardness: 5-5.5                                                      Density: 4.37

Streak/Color: yellow-brown / yellow-brown

Luster: adamantine to dull-earthy

Cleavage/fracture: {010} perfect

Habit: massive, accicular

Other: weathers on hematite

Importance/Uses: iron-ore

*mineraloid, samples are mostly Goethite

Name: Bauxite*                                            Formula: AlO(OH)

Mineral Group: hydroxide                                     Crystal Class: mono/ortho

Hardness: 1-3                                                         Density: 2-2.55

Streak/Color: white-gray / white-gray-pink-red

Luster: dull to earthy

Cleavage/fracture:

Habit: pisolitic, round concretionary grains

Other:

Importance/Uses: aluminum-ore

*mineraloid, samples are mostly Gibbsite & Diaspore

Name: Corundum                                        Formula: Al₂O₃

Mineral Group: oxide                                            Crystal Class: hexagonal

Hardness: 9                                                            Density: 4.02

Streak/Color: white / brown-pink-red-blue

Luster: adamantine to vitreous

Cleavage/fracture: {0001} parting

Habit: tabular (hexagonal prisms)

Other:

Importance/Uses: gemstone (ruby, sapphire), abrasive (emery)

Name: Chromite                                          Formula: FeCr₂O₄

Mineral Group: oxide                                            Crystal Class: isometric

Hardness: 5.5                                                         Density: 4.6

Streak/Color: dark brown / black

Luster: metallic to submetallic

Cleavage/fracture: irregular

Habit: massive, octahedrons

Other: associated with olivine in dunites

Importance/Uses: chromium-ore

Name: Pyrolusite                                      Formula: MnO₂

Mineral Group: oxide                                            Crystal Class: tetragonal

Hardness: 1-2                                                         Density: 4.75

Streak/Color: black / black

Luster: metallic

Cleavage/fracture: {110} perfect, splintery

Habit: dendritic or massive

Other: often sooty

Importance/Uses: manganese-ore

Name: Uraninite                                         Formula: UO₂

Mineral Group: oxide                                            Crystal Class: isometric

Hardness: 5.5                                                         Density: 7.5-9.7

Streak/Color: brown-black / black

Luster: submetallic to pitch-like

Cleavage/fracture: irregular

Habit: massive or botryoidal

Other: radioactive, also known as Pitchblende

Importance/Uses: uranium-ore

Name: Cassiterite                                     Formula: SnO₂

Mineral Group: oxide                                            Crystal Class: tetragonal

Hardness: 6-7                                                         Density: 6.8-7.1

Streak/Color: white / brown-black

Luster: adamantine to submetallic

Cleavage/fracture: {010} imperfect

Habit: prisms, dipyramids

Other:

Importance/Uses: tin-ore

Name: Rutile                                                  Formula: TiO₂

Mineral Group: oxide                                            Crystal Class: tetragonal

Hardness: 6-6.5                                                      Density: 4.2

Streak/Color: pale brown / red-brown to black

Luster: adamantine to submetallic

Cleavage/fracture: {110} distinct

Habit: prismatic, fibrous

Other: often found as fibers growing in quartz and mica

Importance/Uses: titanium-ore

Name: Sylvite                                               Formula: KCl

Mineral Group: halide                                           Crystal Class: isometric

Hardness: 2                                                            Density: 1.99

Streak/Color: colorless / colorless

Luster: transparent

Cleavage/fracture: perfect cubic {001}

Habit: cubes and octahedrons

Other: bitter taste, readily soluble in water

Importance/Uses: K for fertilizer, "salt-substitute"

Name: Gypsum                                                Formula: CaSO₄·2H₂O

Mineral Group: sulfate                                          Crystal Class: monoclinic

Hardness: 2                                                            Density: 2.32

Streak/Color: white / colorless, white, gray

Luster: vitreous to pearly to silky

Cleavage/fracture: 4 directions; {010} perfect, {100} good, 2 para to {111} prism

Habit: tabular, diamond-shaped, fibrous, swallowtail twins

Other:

Importance/Uses: wall board, cement, plaster

Varietal names satin spar (fibrous), selenite (water-clear)

Name: Anhydrite                                        Formula: CaSO₄

Mineral Group: sulfate                                          Crystal Class: orthorhombic

Hardness: 3-3.5                                                      Density: 2.95

Streak/Color: white / colorless, white, pale blue

Luster: vitreous to pearly

Cleavage/fracture: {010} perfect, 3 at right angles

Habit: thick tabular, usually massive

Other:

Importance/Uses: wall board, soil conditioner, sulfuric acid

Name: Barite                                                  Formula: BaSO₄

Mineral Group: sulfate                                          Crystal Class: orthorhombic

Hardness: 3-3.5                                                      Density: 4.5

Streak/Color: white / colorless, white to light blue and yellow

Luster: vitreous to pearly

Cleavage/fracture: {001} perfect

Habit: tabular, "desert roses"

Other:

Importance/Uses: drilling mud, source of barium

Name: Celestite                                         Formula: SrSO₄

Mineral Group: sulfate                                          Crystal Class: orthorhombic

Hardness: 3-3.5                                                      Density: 3.96

Streak/Color: white / colorless to light blue

Luster: vitreous to pearly

Cleavage/fracture: {001} perfect

Habit: tabular

Other:

Importance/Uses: source of strontium

Name: Aragonite                                       Formula: CaCO₃

Mineral Group: carbonate                                     Crystal Class: orthorhombic

Hardness: 3.5-4                                                      Density: 2.94

Streak/Color: white / white, yellow, pink

Luster: vitreous

Cleavage/fracture: {010} distinct

Habit: acicular pyramidal, tabular, pseudohexagonal twins

Other: effervesces in cold, dilute HCl

Importance/Uses: hard parts of many marine animals

Image may differ

Name: Siderite                                             Formula: FeCO₃

Mineral Group: carbonate                                     Crystal Class: hexagonal

Hardness: 3.5-4                                                      Density: 3.96

Streak/Color: light brown / light to dark brown

Luster: vitreous

Cleavage/fracture: perfect rhombic

Habit: rhombohedron with curved faces

Other:

Importance/Uses: iron-ore

Name: Rhodochrosite                           Formula: MnCO₃

Mineral Group: carbonate                                     Crystal Class: hexagonal

Hardness: 3.5-4                                                      Density: 3.6

Streak/Color: white / pink

Luster: vitreous

Cleavage/fracture: perfect rhombic

Habit: massive

Other:

Importance/Uses: minor Mn-ore, jewelry

Name: Azurite                                               Formula: Cu₃(CO₃)₂(OH)₂

Mineral Group: carbonate                                     Crystal Class: monoclinic

Hardness: 3.5-4                                                      Density: 3.77

Streak/Color: 'azure'-blue / 'azure'-blue

Luster: vitreous

Cleavage/fracture: {011} perfect

Habit: often malformed

Other: effervescence in HCl, found with malachite

Importance/Uses: copper-ore

Name: Malachite                                       Formula: Cu₂CO₃(OH)₂

Mineral Group: carbonate                                     Crystal Class: monoclinic

Hardness: 3.5-4                                                      Density: 4.0

Streak/Color: pale green / bright green

Luster: adamantine to vitreous

Cleavage/fracture: {201} perfect

Habit: radiating fibers, botryoidal forms

Other: effervescence in HCl, found with azurite

Importance/Uses: copper-ore, jewelry/ornamental

Green Mineral

Name: Apatite                                               Formula: Ca₅(PO₄)₃(F,Cl,OH)

Mineral Group: phosphate                                     Crystal Class: hexagonal

Hardness: 5                                                            Density: 3.2

Streak/Color: white / light green to red-brown

Luster: vitreous to subresinous

Cleavage/fracture: {0001} poor

Habit: long-hexagonal prisms terminated with dipyramid

Other:

Importance/Uses: fertilizer, phosphoric acid, teeth & bones

Name: Olivine                                        Formula: (Fe,Mg)₂SiO₄

Mineral Group: orthosilicate                         Crystal Class: orthorhombic

Hardness: 6.5-7                                               Density: 3.22-4.39

Streak/Color: white / pale yellow-green to olive-green

Luster: vitreous

Cleavage/fracture: poor to none / conchoidal

Habit: three prisms, three pinacoids and a dipyramid

Other: often found in granular masses

Occurrence/Uses: mafic/ultramafic ig rock, upper mantle rocks

Fayalite (Fe) - Forsterite (Mg) solid-solution series

Name: Garnet                                        Formula: X₃Al₂(SiO₄)₃

Mineral Group: orthosilicate                         Crystal Class: isometric

Hardness: 6.5-7.0                                            Density: 3.1-4.2

Streak/Color: white / green, red, brown

Luster: vitreous to resinous

Cleavage/fracture: none / subconchoidal

Habit: distinct dodecahedrons and trapezohedrons

Other:

Occurrence/Uses: meta rocks / abrasive, gemstone

Varieties: X = Ca-Grossular, Mg-Pyrope, Fe-Almandine

Name: Kyanite                                       Formula: Al₂SiO₅

Mineral Group: orthosilicate                         Crystal Class: triclinic

Hardness: 5 / 7                                                Density: 3.55-3.67

Streak/Color: white / light blue, white

Luster: vitreous to pearly

Cleavage/fracture: {100} perfect / splintery

Habit: elongated tabular, bladed aggregates

Other: hardness varies with crystal direction

Occurrence/Uses: regional pelitic (Al-rich) meta rocks

Polymorph of sillimanite and andalusite

Name: Diopside                                      Formula: CaMg(SiO₃)₂

Mineral Group: inosilicate                             Crystal Class: monoclinic

Hardness: 5.5-6.5                                            Density: 3.27

Streak/Color: white / white to green

Luster: vitreous

Cleavage/fracture: two on {110} at ~90° / uneven

Habit: stout prismatic

Other: part of augite-hedenbergite solid solution series

Occurrence/Uses: meta impure carbonates (skarns)

Clinopyroxene (single chain)

Name: Augite                                          Formula: (Ca,Mg,Fe,Al)₂(SiO₃)₂

Mineral Group: inosilicate                             Crystal Class: monoclinic

Hardness: 5.5-6                                               Density: 3.19-3.56

Streak/Color: white-gray / green to black

Luster: vitreous to dull

Cleavage/fracture: two on {110} at ~90° / uneven

Habit: short prismatic

Other: part of diopside-hedenbergite solid solution series

Occurrence/Uses: intrusive mafic ig rocks, mafic meta rocks

Clinopyroxene (single chain)

Name: Enstatite                                  Formula: (Mg,Fe)₂(SiO₃)₂

Mineral Group: inosilicate                             Crystal Class: orthorhombic

Hardness: 5-6                                                  Density: 3.21-3.96

Streak/Color: white-gray / brown, green, black

Luster: vitreous to pearly

Cleavage/fracture: two on {210} at ~90° / uneven

Habit: stout prismatic

Other:

Occurrence/Uses: mafic/ultramafic ig rocks, granulites

Orthopyroxene (single chain)

Name: Hornblende                            Formula: (Na,K)Ca₂(Mg,Fe,Al)₅Si₈O₂₂(OH)₂

Mineral Group: inosilicate                             Crystal Class: monoclinic

Hardness: 5-6                                                  Density: 3.02-3.59

Streak/Color: gray-green / green, dark green, black

Luster: vitreous

Cleavage/fracture: two on {110} at 56 & 124° / irregular

Habit: slender prismatic, diamond-shaped in cross section

Other: considerable variation in composition

Occurrence/Uses: intermediate ig. and mafic meta. rocks

Amphibole (double chain)

Name: Tremolite                                Formula: Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂

Mineral Group: inosilicate                             Crystal Class: monoclinic

Hardness: 5-6                                                  Density: 2.99-3.48

Streak/Color: white / colorless, light green

Luster: vitreous

Cleavage/fracture: two on {110} at 56 & 124° / irregular

Habit: columnar, bladed, or accicular

Other: solid solution with actinolite (Fe)

Occurrence/Uses: contact & regional meta carbonates

Amphibole (double chain)

Name: Actinolite                               Formula: Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂

Mineral Group: inosilicate                             Crystal Class: monoclinic

Hardness: 5-6                                                  Density: 2.99-3.48

Streak/Color: white / green

Luster: vitreous

Cleavage/fracture: two on {110} at 56 & 124° / irregular

Habit: columnar, bladed, or accicular

Other: solid solution with tremolite (Mg)

Occurrence/Uses: contact & regional meta carbonates

Amphibole (double chain)

Name: Muscovite                                Formula: KAl₂(AlSi₃O₁₀)(OH,F,Cl)₂

Mineral Group: phyllosilicate                        Crystal Class: monoclinic

Hardness: 2.5 / 4                                             Density: 2.77-2.88

Streak/Color: white / colorless to light green, red, brown

Luster: vitreous

Cleavage/fracture: perfect basal {001}

Habit: tabular with pseudohexagonal forms, 'books'

Other: Sericite is fine-grained hydrothermal alteration form

Occurrence/Uses: granitic ig rocks, wide range of meta rocks / isinglass, electronics, cosmetics, plastics, etc

Mica

Name: Biotite                                         Formula: K(Fe,Mg)₃AlSi₃O₁₀(OH)₂

Mineral Group: phyllosilicate                        Crystal Class: monoclinic

Hardness: 2-3                                                  Density: 2.7-3.3

Streak/Color: white-gray / black or dark bown

Luster: vitreous

Cleavage/fracture: perfect basal {001}

Habit: tabular with pseudohexagonal outlines, 'books'

Other: solid solution with phlogopite (Mg)

Occurrence/Uses: common in wide range of ig and meta rocks / vermiculite is altered biotite

Mica

Name: Phlogopite                              Formula: KMg₃AlSi₃O₁₀(OH)₂

Mineral Group: phyllosilicate                        Crystal Class: monoclinic

Hardness: 2.5                                                  Density: 2.78

Streak/Color: white / light brown

Luster: vitreous

Cleavage/fracture: perfect basal {001}

Habit: tabular with pseudohexagonal outlines, 'books'

Other: part of biotite solid solution series (Fe-Mg)

Occurrence/Uses: mafic/ultramafic ig rocks, meta carbonates

Name: Talc                                               Formula: Mg₂Si₄O₁₀(OH)₂

Mineral Group: phyllosilicate                        Crystal Class: triclinic

Hardness: 1                                                     Density: 2.58-2.83

Streak/Color: white / white, light green, light brown

Luster: pearly to greasy

Cleavage/fracture: perfect basal {001}

Habit: foliated, radiating irregular flakes or fibers

Other: waxy feel, sectile

Occurrence/Uses: hydrothermal alteration of mafic/ultramafic ig rocks / paint, plastics, paper, lubricant, etc

Name: Serpentine                               Formula: Mg₃Si₂O₅(OH)₄

Mineral Group: phyllosilicate                        Crystal Class: monoclinic

Hardness: 2.5-3.5                                            Density: 2.55-2.65

Streak/Color: white / shades of green

Luster: greasy to waxy, silky

Cleavage/fracture: perfect {001} in antigorite form

Habit: fine silky fibers, fine-grained massive, scaly masses

Other: Asbestos is type of serpentine (chrysotile)

Occurrence/Uses: hydrothermal alteration of mafic/ultramafic ig rocks / brake shoes, insulation, floor tiles

Green Mineral

Name: Kaolinite                                  Formula: Al₂Si₂O₅(OH)₄

Mineral Group: phyllosilicate                        Crystal Class: triclinic

Hardness: 2-2.5                                               Density: 2.61-2.68

Streak/Color: white / white

Luster: pearly to dull earthy

Cleavage/fracture: perfect {001}

Habit: very minute, thin, rhombic or hexagonal plates, massive

Other:

Occurrence/Uses: weathering product of feldspar / ceramics, pottery, filler in paper, etc

Clay      

Name: Chlorite                     Formula: (Mg,Fe,Al)₃(Si,Al)₄O₁₀(OH)₂(Mg,Fe,Al)₃(OH)₆

Mineral Group: phyllosilicate                        Crystal Class: monoclinic

Hardness: 2-3                                                  Density: 2.6-3.3

Streak/Color: greenish white to white / shades of green

Luster: vitreous to pearly, waxy, or dull

Cleavage/fracture: perfect {001}

Habit: fine grained scaly or foliated masses

Other:

Occurrence/Uses: widespread in low-medium grade pelitic and mafic meta rocks and altered ig rocks

Name: Beryl                                            Formula: Be₃Al₂Si₆O₁₈

Mineral Group: cyclosilicate                          Crystal Class: hexagonal

Hardness: 7.5-8                                               Density: 2.63-2.97

Streak/Color: white / blue-green, yellow, pink

Luster: vitreous

Cleavage/fracture: {0001} imperfect, conchoidal

Habit: hexagonal {100} prisms

Other:

Occurrence/Uses: granitic pegmatites / Beryllium-ore, gemstone (blue = aquamarine, green = emerald)

Name: Tourmaline              Formula: Na(Mg,Fe,Li,Al)₃Al₆Si₆O₁₈(BO₃)₃(O,OH,F)₄

Mineral Group: cyclosilicate                          Crystal Class: hexagonal

Hardness: 7                                                     Density: 2.9-3.22

Streak/Color: white-gray / black-brown, green, pink

Luster: vitreous

Cleavage/fracture: very poor / conchoidal

Habit: vertically striated trigonal prisms

Other: strongly piezoelectric

Occurrence/Uses: granitic pegmatites / gemstone (black = schorl, pink = rubellite)

many varities

Name: Epidote                                        Formula: Ca₂(Al,Fe)Al₂O(SiO₄)(Si₂O₇)(OH)

Mineral Group: sorosilicate                           Crystal Class: monoclinic

Hardness: 6-7                                                  Density: 3.21-3.49

Streak/Color: white / yellowish green to black

Luster: vitreous

Cleavage/fracture: one on {001} perfect / uneven

Habit: elongated prismatic, granular masses

Other:

Occurrence/Uses: regional & contact meta, low-temperature deuteric alteration

Name: Quartz                                         Formula: SiO₂

Mineral Group: tectosilicate                          Crystal Class: hexagonal

Hardness: 7                                                     Density: 2.64

Streak/Color: white / colorless, white, purple, pink, black

Luster: vitreous

Cleavage/fracture: poor / conchoidal

Habit: hexagonal prisms, trigonal dipyramids

Other: many varieties/forms (chert, flint, amethyst, milky, etc)

Occurrence/Uses: felsic to intermediate ig & meta rocks, clastic sed rocks / foundry sand to glass, etc

Name: Potassium Feldspars      Formula: KAlSi₃O₈

Name: Orthoclase                            Formula: KAlSi₃O₈

Mineral Group: tectosilicate                          Crystal Class: monoclinic

Hardness: 6-6.5                                               Density: 2.54-2.63

Streak/Color: white / white, gray, pink

Luster: vitreous

Cleavage/fracture: perfect {001}, good {010} at ~90°

Habit: elongate, Carlsbad twins

Other: schiller or opalescence

Occurrence/Uses: granitic rocks / porcelain

Potassium feldspar polymorph

Name: Microcline                             Formula: KAlSi₃O₈

Mineral Group: tectosilicate                          Crystal Class: triclinic

Hardness: 6-6.5                                               Density: 2.54-2.63

Streak/Color: white / white, gray, pink, blue-green

Luster: vitreous

Cleavage/fracture: perfect {001}, good {010} at ~90°

Habit: tabular and elongate

Other: exsolution lamellae, polysynthetic twinning

Occurrence/Uses: intrusive ig and meta rocks / porcelain

Potassium feldspar polymorph

Name: Sanidine                                      Formula: KAlSi₃O₈

Mineral Group: tectosilicate                          Crystal Class: monoclinic

Hardness: 6-6.5                                               Density: 2.54-2.63

Streak/Color: white / colorless to white

Luster: vitreous

Cleavage/fracture: perfect {001}, good {010} at ~90°

Habit: tabular Carlsbad twins

Other:

Occurrence/Uses: extrusive silicic ig rocks

Potassium feldspar polymorph

Name: Plagioclase Feldspars     Formula: NaAlSi₃O₈ - CaAl₂Si₂O₈

Mineral Group: tectosilicate                                 Crystal Class: triclinic

Hardness: 6-6.5                                                      Density: 2.60-2.67

Streak/Color: white / white-gray, blue

Luster: vitreous to pearly

Cleavage/fracture: basal {001} perfect, {010} good at ~90°

Habit: tabular and elongate

Other: iridescence, striations on basal cleavage

Occurrence/Uses: granitic to mafic rocks / ceramics

Plagioclase from Na- to Ca-rich: Albite - Oligoclase - Andesine - Labradorite - Bytownite - Anorthite

Name: Albite                                           Formula: NaAlSi₃O₈

Mineral Group: tectosilicate                          Crystal Class: triclinic

Hardness: 6-6.5                                               Density: 2.60

Streak/Color: white / white-gray, blue

Luster: vitreous to pearly

Cleavage/fracture: basal {001} perfect, {010} good at ~90°

Habit: tabular and elongate

Other: iridescence, striations on basal cleavage

Occurrence/Uses: granitic to intermediate ig rocks / ceramics

Plagioclase feldspar series

Name: Anorthite                                Formula: CaAl₂Si₂O₈

Mineral Group: tectosilicate                          Crystal Class: triclinic

Hardness: 6-6.5                                               Density: 2.76

Streak/Color: white / white-gray, blue

Luster: vitreous to pearly

Cleavage/fracture: basal {001} perfect, {010} good at ~90°

Habit: tabular, prismatic

Other: iridescence, striations on basal cleavage

Occurrence/Uses: mafic to intermediate ig rocks / ornamental

Plagioclase feldspar series

Name: Leucite                                       Formula: KAlSi₂O₆

Mineral Group: tectosilicate                          Crystal Class: tetragonal

Hardness: 5.5-6                                               Density: 2.45-2.50

Streak/Color: white / white to gray

Luster: vitreous

Cleavage/fracture: poor / conchoidal

Habit: equant trapezohedral 8-sided crystals

Other:

Occurrence/Uses: recent silica deficient lavas

Feldspathoid

Name: Sodalite                                     Formula: Na₈Al₆Si₆O₂₄Cl₂

Mineral Group: tectosilicate                          Crystal Class: isometric

Hardness: 5.5-6                                               Density: 2.27 - 2.33

Streak/Color: white / light to dark blue

Luster: vitreous

Cleavage/fracture: poor / uneven to conchoidal

Habit: massive, rare dodecahedrons

Other: associated with nepheline and cancrinite

Occurrence/Uses: alkali-rich, silica-poor ig rocks / ornamental

Name: Nepheline                                 Formula: Na₃KAl₄Si₄O₁₆

Mineral Group: tectosilicate                          Crystal Class: hexagonal

Hardness: 5.5-6                                               Density: 2.55-2.67

Streak/Color: white / white-gray

Luster: subvitreous to greasy

Cleavage/fracture: poor / conchoidal

Habit: anhedral masses

Other: associated with sodalite and cancrinite

Occurrence/Uses: alkali-rich, silica-poor ig rocks / glaze, ceramics, glass

Feldspathoid                                     

Name: Sillimanite                             Formula: Al₂SiO₅

Mineral Group: orthosilicate                         Crystal Class: orthorhombic

Hardness: 6.5-7.5                                            Density: 3.23-3.27

Streak/Color: white / white, brown, pale green

Luster: vitreous

Cleavage/fracture: {010} perfect / uneven

Habit: prismatic, fibrous

Other:

Occurrence/Uses: high temp pelitic (Al- rich) meta rocks

Polymorph of kyanite and andalusite

Name: Andalusite                              Formula: Al₂SiO₅

Mineral Group: orthosilicate                         Crystal Class: orthorhombic

Hardness: 6.5-7.5                                            Density: 3.13-3.16

Streak/Color: white / pink, white, pinkish brown, violet

Luster: vitreous

Cleavage/fracture: good {110} prismatic at ~90° / uneven

Habit: prismatic elongate 

Other: chiastolite form has cross along diagonals of prism

Occurrence/Uses: contact pelitic meta rocks / refractory

Polymorph of sillimanite and kyanite

Name: Staurolite                              Formula: Fe₂Al₉O₆(SiO₄)₄(OH)₂

Mineral Group: orthosilicate                         Crystal Class: monoclinic

Hardness: 7-7.5                                               Density: 3.74-3.83

Streak/Color: gray / brown

Luster: vitreous

Cleavage/fracture: poor / subconchoidal

Habit: prismatic and elongate, cross-shaped penetration twins

Other:

Occurrence/Uses: medium grade pelitic meta rocks / abrasive

Name: Topaz                                             Formula: Al₂(F,OH)₂SiO₄

Mineral Group: orthosilicate                         Crystal Class: orthorhombic

Hardness: 8                                                     Density: 3.49-3.57

Streak/Color: white / colorless, yellow, pink, brown, etc

Luster: vitreous

Cleavage/fracture: basal {001} perfect / subconchoidal

Habit: stubby to elongate prisms

Other:

Occurrence/Uses: felsic ig rocks, hydrothermally altered granites / gemstone

Name: Wollastonite                      Formula: CaSiO₃

Mineral Group: inosilicate                             Crystal Class: triclinic

Hardness: 4.5-5                                               Density: 2.86-3.09

Streak/Color: white / white, gray, pale green

Luster: vitreous

Cleavage/fracture: perfect {100} good {001} at ~90° / uneven

Habit: bladed, columnar, fibrous

Other:

Occurrence/Uses: meta carbonates / asbestos replacement, paint, ceramics

Pyroxenoid

Name: Natrolite                                 Formula: Na₂Al₂Si₃O₁₀ · 2H₂O

Mineral Group: tectosilicate                          Crystal Class: orthorhombic

Hardness: 5                                                     Density: 2.25

Streak/Color: white / white, gray, bluish, yellowish

Luster: vitreous

Cleavage/fracture: {110} perfect

Habit: prismatic to acicular, radiating aggregates

Other: often too fine-grained to ID in handsample

Occurrence/Uses: lining cavities in basalt / catalysts, filters, soil conditioner, filters, cation exchangers, etc

Zeolite

Name: Zircon                                          Formula: ZrSiO₄

Mineral Group: orthosilicate                         Crystal Class: tetragonal

Hardness: 7.5                                                  Density: 4.68

Streak/Color: white / grayish, yellowish or reddish brown

Luster: subadamantine

Cleavage/fracture: {110} and {111} poor / conchoidal

Habit: tetragonal prismatic with dipyramidal terminations

Other:

Occurrence/Uses: widespread accessory mineral / source of zirconium and hafnium

Name: Titanite                                      Formula: CaTiSiO₅

Mineral Group: orthosilicate                         Crystal Class: monoclinic

Hardness: 5-5.5                                               Density:

Streak/Color: white  / brown, gray, green, yellow, red, black

Luster: adamantine to resinous

Cleavage/fracture: good prismatic {110} / uneven

Habit: wedge-shaped

Other: formerly called sphene

Occurrence/Uses: common accessory mineral in ig rocks / titanium ore