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Conversations with the Earth Tom Burbine tburbine@framingham.edu. Mineral. A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystal structure ~4,000 known minerals Of these, perhaps 100 can be called "common"
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Conversations with the EarthTom Burbinetburbine@framingham.edu
Mineral • A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystal structure • ~4,000 known minerals • Of these, perhaps 100 can be called "common" • 50 are "occasional“ • rest are "rare" to "extremely rare".
Quartz – SiO2 • Diamond – C • Graphite– C • Calcite – CaCO3 • Talc - Mg3Si4O10(OH)2
Is ice a mineral? • Yes, as long as it was made inorganically
Crystal Structure • Crystalline structure - orderly three-dimensional arrangement of atoms or molecules • Forms crystals
Color • Usually the most noticeable property • Sometimes minerals can have a wide variety of colors
Clarity • Transparent – clear • Translucent – foggy • Opaque – light doesn’t travel through
Crystal Form • Perfectly grown crystals can have a perfect crystal form (e.g., cube, pyramid, prism)
Luster • How light reflects from a mineral • Metallic luster – reflects like a metal • Nonmetallic luster – doesn’t reflect like a metal • Vitreous – like a glossy photograph • Waxy – like the luster of a candle • Satiny – like the luster of satin • Earthy – like dry soil • Greasy – like the luster of grease • Porcelaneous – like the luster of porcelain
Streak • Color of a substance as a fine powder • A mineral is scratched on a streak plate
Hardness • Mohs Hardness scale • 1-10 scale • Hard minerals- can scratch glass • Soft minerals – • can’t scratch glass Streak Plate Penny
Cleavage • Cleavage – tendency of some minerals to break along flat, parallel surfaces • Cleavage planes are parallel surfaces of weak chemical bonding • Fracture is a break in a mineral does not occur along a cleavage plane
Tenacity • Tenacity - resists breakage • Brittle – shatters like glass • Malleable – like clay • Elastic – like a plastic comb • Sectile – carved with a knife
Reaction with acid • Fizzes with cool, dilute hydrochloric acid • Carbonate minerals (minerals with CO3) • Calcite readily fizzes • Dolomite will only fizz if powdered
Striations • Straight, hairline grooves on the cleavage surfaces • Plagioclase feldspar has striations
Magnetism • Magnetic • Magnetite is magnetic
Specific gravity • Density of a substance divided by the density of water • e.g., quartz has a specific gravity of 2.65