Conversations with the Earth Tom Burbine tburbineframingham edu
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" – 50 are "occasional“ – rest are "rare" to "extremely rare".
• Earth is made of minerals
• Can you name any minerals?
• • • Quartz – Si. O 2 Diamond – C Graphite– C Calcite – Ca. CO 3 Talc - Mg 3 Si 4 O 10(OH)2
Is ice a mineral?
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 mineralscan 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 CO 3) 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
Any Questions?
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