Earth & Space Science Chapter 4 Minerals
Mineral Characteristics Naturally occurring Inorganic (has never been alive) Solid Specific chemical composition (can be an element or a compound) Atoms are arranged in a regular crystal structure Name some minerals…. Is coal a mineral? Salt? Sugar? Glacial ice? Natural gas? Diamond?
How Minerals Form Molten magma cools and crystallizes – If cooling is slow, large crystals form – If cooling is fast, small crystals form Minerals can form from solutions – Water can evaporate, leaving mineral crystals behind – Minerals can precipitate from a saturated solution
Mineral Identification Luster (metallic or nonmetallic)
Mineral Identification Color (not always reliable for identification)
Mineral Identification Streak color (scrape against a ceramic tile)
Mineral Identification Hardness (how easily it is scratched)
Mineral Identification Cleavage/fracture (does it break evenly or with jagged edges
Mineral Identification Texture How does it feel? (smooth, rough, glassy, soapy, greasy) Feel these minerals: – Quartz (smooth/glassy) – Graphite (greasy) – Talc (soapy)
Mineral Identification Crystal structure
Mineral Identification Specific Gravity/Density
California in 1849…. How would you tell the difference between gold and pyrite (fool’s gold)?
Special Properties Taste (halite) Smell (sulfur) Magnetism (magnetite) Double refraction (calcite-Iceland spar) Effervescence—bubbles—in acid (calcite/carbonates) Fluorescence—glow in the dark (fluorite) Iridescence—color changing (labradorite, bornite)
Mineral Groups Sharing similar chemical composition: Silicates: quartz, feldspar, mica Carbonates: calcite, dolomite, azurite Metal oxides: hematite, magnetite Others: – Sulfides: pyrite – Halides: halite – Native elements: copper, silver, etc.
Economically Important Minerals Ore: a mineral that contains a useful substance that can be mined profitably – Hematite (iron) – Bauxite (aluminum) Gem: a mineral prized for its rarity and beauty – Ruby – Emerald – Diamond