Earth & Space ScienceChapter 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