Page 112 - Laboratory Manual in Physical Geology

MINERAL DATABASE (Alphabetical Listing)

Luster and
Mineral Crystal Hardness Streak Distinctive Some Uses
System Properties
PYROXENE: See AUGITE
QUARTZ Nonmetallic 7 White* Usually colorless, white, or gray but Used as an abrasive;
(NM) uncommon varieties occur in all colors; Used to make glass,
SiO 2
silicon dioxide Transparent to translucent; Luster gemstones
greasy; No cleavage; Forms hexagonal
Hexagonal prism and pyramids; SG = 2.6–2.7
Some quartz varieties are:
• var. flint (opaque black or dark gray)
• var. smoky (transparent gray)
• var. citrine (transparent yellow-brown)
• var. amethyst (purple)
• var. chert (opaque gray)
• var. milky (white)
• var. jasper (opaque red or yellow)
• var. rock crystal (colorless)
• var. rose (pink)
• var. chalcedony (translucent, waxy
luster)
SERPENTINE Nonmetallic 2–5 White Color pale or dark green, yellow, Fibrous varieties used for
(NM) gray; Forms dull or silky masses fire-resistant clothing,
Mg 6 Si 4 O 10 (OH) 8
magnesium silicate and asbestos forms; No cleavage; tiles, brake linings
hydroxide Monoclinic SG = 2.2–2.6
SILLIMANITE Nonmetallic 6–7 White Color pale brown, white, or gray; High-temperature
Al 2 (SiO 4 )O (NM) One good cleavage plus fracture ceramics
aluminum silicate surfaces; Forms slender prisms
Orthorhombic and needles; SG = 3.2

SILVER Metallic 2.5–3.0 White to Color silvery white to gray; Tarnishes Ductile and malleable
(NATIVE SILVER) (M) silvery white dark gray to black; Ductile, malleable metal used for jewelry and
Ag and sectile; Hackly fracture; No silverware; Electrical circuit
pure silver cleavage; Forms nuggets, curled boards for computers and
Isometric wires, and dendritic forms; SG = 10.5 cell phones; Photographic
film
SPHALERITE Metallic (M) 3.5–4 White to pale Color silvery yellow-brown, dark red, Ore of zinc for brass,
ZnS or yellow-brown or black; Tarnishes brown or black; galvanized steel and
zinc sulfide Nonmetallic Dodecahedral cleavage excellent to roofing nails, skin-healing
(NM) good; Smells like rotten eggs when creams, pills for healthy
scratched/powdered; Forms immune system and
misshapen tetrahedrons or protein production: Ore of
Isometric dodecahedrons; SG = 3.9–4.1 Indium (an impurity) used
to make solar cells
STAUROLITE Nonmetallic 7 White to Color brown to gray-brown; Tarnishes Gemstone crosses
iron magnesium (NM) gray* dull brown; Forms prisms that called “fairy crosses”
zinc aluminum interpenetrate to form natural crosses;
silicate Monoclinic Cleavage poor; SG = 3.7–3.8

SULFUR Nonmetallic 1.5–2.5 Pale yellow Color bright yellow; Forms Used for matches,
(NATIVE SULFUR) (NM) transparent to translucent gunpowder, fertilizer, rubber
S crystals or earthy masses; hardening (car tires),
sulfur Cleavage poor; Luster greasy to fungicide, insecticide,
Orthorhombic
earthy; Brittle; SG = 2.1 paper pulp processing
TALC Nonmetallic 1 White Color white, gray, pale green, or Used as a “filler” (to take
(NM) brown; Forms cryptocrystalline up space and reduce cost)
Mg 3 Si 4 O 10 (OH) 2
hydrous magnesian masses that show no cleavage; in plastics for car parts,
silicate Luster silky to greasy; Feels appliances; Massive
greasy or soapy (talcum powder); pieces carved into art
Monoclinic
Very soft; SG = 2.7–2.8 sculptures
TOURMALINE Nonmetallic 7–7.5 White* Color usually opaque black or green, Crystals used in radio
complex silicate (NM) but may be transparent or transmitters; gemstone
translucent green, red, yellow, pink
or blue; Forms long striated prisms
with triangular cross sections;
Hexagonal
Cleavage absent; SG = 3.0–3.2
ZEOLITE: A group of calcium or sodium hydrous aluminum silicates. See NATROLITE.
*Streak cannot be determined with a streak plate for minerals harder than 6.5. They scratch the streak plate.

Mineral Properties, Identification, and Uses ■ 97