Minerals Flashcards
Brass color, H 6-6.5, conchoidal to uneven fracture that creates cubes, Dark or grey streak
Pyrite
Silvery grey to black color, H 6-6.5, strongly attracted to a magnet, fracture
Magnetite
Color silvery black to black; tarnishes gray to black; H 5.5–6; maybe weakly attracted to a magnet; forms octahedrons, absent cleavage
Chromite
Color steel gray, reddish-silver, to glittery bright silver (var. specular); both metallic varieties have the characteristic red-brown streak; may be attracted to a magnet; H 5–6; also occurs in nonmetallic, dull to earthy, red to red-brown streak
Hematite
Color bright silvery gray; tarnishes dull gray; brittle: breaks into cubes and shapes made of cubes; H 2.5; forms cubes or octahedrons; feels heavy for its size because of high specific gravity
Galena
Color bright silvery gold; tarnishes bronze brown brassy gold, or iridescent blue-green and red; H 3.5–4.0; brittle; uneven fracture; forms tetrahedrons
Chalcopyrite
Color opaque brassy to brown-bronze; tarnishes dull brown, may have faint iridescent colors; fracture uneven to conchoidal; no cleavage; attracted to a magnet; H 3.5–4.5; usually massive or masses of tiny crystals; resembles chalcopyrite, which is softer and not attracted to a magnet
Pyrrhotite
Color dark silvery gray to black; can be scratched with your fingernail; easily rubs off on your fingers and clothes, making them gray; H 1–2
Graphite
Metallic or silky submetallic luster, color dark brown, gray, or black; H 5–5.5; forms layers of radiating microscopic crystals and botryoidal masses
Goethite
Color copper; tarnishes dull brown or green; H 2.5–3.0; malleable and sectile; hackly fracture; usually forms dendritic masses or nuggets
Copper
Translucent to opaque dark gray; blue-gray, or black; may have silvery iridescence; 2 cleavages at nearly 90° and with striations; H 6
Plagioclase feldspar
Translucent to opaque dark gray; blue-gray, or black; may have silvery iridescence; 2 cleavages at nearly 90° and with striations; H 6
Potassium feldspar
Transparent or translucent gray, brown, or purple; vitreous luster; massive or hexagonal prisms and pyramids; H 7, absent cleavage
Quartz
Gray, black, or colored (dark red, blue, brown) hexagonal prisms with flat striated ends; H 9, absent cleavage
Corundum
Transparent to translucent dark red to black; equant (dodecahedron) crystal form or massive; H 7
Garnet
Black or dark green; long striated prisms; H 7–7.5
Tourmaline
Olive green, transparent or translucent; no cleavage; usually has many cracks and conchoidal to uneven fracture; single crystals or masses of tiny crystals resembling green granulated sugar or aquarium gravel; the crystals have vitreous (glassy) luster
Olivine
Opaque green; poor cleavage; H 6–7
Epidote
Purple cubes or octahedrons; octahedral cleavage; H 4
Fluorite
Black short opaque prisms; splits easily along 1 excellent cleavage into thin sheets; H 2.5–3
Biotite
Green short opaque prisms; splits easily along 1 excellent cleavage into thin sheets; H 2–3
Chlorite
Deep blue; crusts, small crystals, or massive; light blue streak; H 3.5–4
Azurite
Green, green-blue, gray, yellow-green, white; platy or tabular or fibrous (chrysotile asbestos); H 2.5–3.5
Serpentine Minerals
Opaque green in laminated crusts or massive; streak pale green; effervesces in dilute HCI; H 3.5–4
Malachite
Translucent or opaque dark green; can be scratched with your fingernail; feels greasy or soapy; H 1
Talc
Transparent or translucent green, brown, blue, or purple; brittle hexagonal prisms; conchoidal fracture; H 5
Apatite
Opaque earthy brick red to dull red-gray, or gray; H 1.5–5; red-brown streak; magnet may attract the gray forms
Hematite
Colorless, white, yellow, green, pink, or brown; 3 excellent cleavages; breaks into rhombohedrons; effervesces in dilute HCI; H 3
Calcite
Colorless, white, yellow, blue, brown, or red; cubic crystals; breaks into cubes; salty taste; H 2.5
Halite
Opaque pale blue to blue-green; conchoidal fracture; H 2–4; massive or amorphous earthy crusts; very light blue streak
Chrysocolla
