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Minerals

Minerals. Minerals vs. Rocks. Rock – an aggregate of minerals (mixture of minerals). Mineral – naturally occurring, inorganic, crystalline solids, with a definite chemical composition. All minerals are rocks, but not all rocks are minerals!. Granite (rock). mixture of:. Quartz

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Minerals

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  1. Minerals

  2. Minerals vs. Rocks • Rock – an aggregate of minerals (mixture of minerals). • Mineral – naturally occurring, inorganic, crystalline solids, with a definite chemical composition. All minerals are rocks, but not all rocks are minerals!

  3. Granite (rock) mixture of: Quartz (mineral) Feldspar (mineral) Biotite (mineral)

  4. Properties of Minerals 1. Crystal Form • External expression of a mineral’s internal orderly arrangement of atoms. • Size of the crystal is based on time & available space.

  5. Crystal Shapes: Hexagonal Tetragonal Cubic Monoclinic Orthorhombic Triclinic

  6. Properties of Minerals 2. Luster • Appearance /quality of light reflected from the surface of a mineral. • Metallic vs. Nonmetallic.

  7. Choosing the Luster: Luster Shiny like a metal? Yes Metallic No Nonmetallic What kind of nonmetallic? Vitreous (glassy) Pearly Silky Resinous Earthy

  8. Properties of Minerals 3. Color • Outer appearance. • Unreliable property. • A mineral may have several color varieties.

  9. Properties of Minerals 4. Streak • Color of the mineral in a powdered form. • Obtained by rubbing the mineral across a streak plate.

  10. Properties of Minerals 5. Hardness • Resistance to abrasion or scratching. Mohs’ Scale Talc Gypsum Calcite Fluorite Apatite Feldspar Quartz Topaz Corundum Diamond Softest Hardest

  11. How to test a mineral’s hardness Start by moving an unknown sample across a sample with a hardness of 1. 2. If the unknown scratches the known sample, then it is harder….so keep testing the others until it doesn’t scratch it. 3. If it doesn’t scratch it, then it is softer than the known sample so it is lower on the scale. 4. If they scratch each other, they are the same hardness.

  12. Properties of Minerals 6. Cleavage • Tendency for a mineral to break along planes of weak bonding. • Smooth surfaces. • Not to be confused with crystals.

  13. Properties of Minerals 7. Fracture • Opposite of cleavage. • Conchoidal fracture = curved edges. • Fibrous fracture = splinters/fibers.

  14. Properties of Minerals 8. Specific Gravity • Comparison between the weight of a mineral to the weight of an equal volume of water. • Comparison of densities. • Written as the number of times heavier/lighter than water.

  15. Properties of Minerals 9. Other Properties • Taste • Elasticity • Malleability • Texture • Magnetism • Double Refraction • Reaction to acids (HCl)

  16. Mineral Groups • 8 elements make up 98% of the Earth’s crust (by weight). • O • Si • Al • Fe • Ca • Na • K • Mg

  17. Mineral Groups • Silicate Group • Minerals made of O and Si. • ¾ of the minerals in the continental crust are silicates. • Silicon-oxygen tetrahedron (1 silicon to 4 oxygen) then bonded to another element(s). • EXAMPLES: • Quartz, Feldspars, Micas

  18. Mineral Groups • Carbonates Group • Minerals made of CO3 bonded with other elements. • EXAMPLES: • Calcite & Dolomite • Halides Group • Minerals made with members of the halogen family. • Formed through evaporation. • EXAMPLES: • Halite & Fluorite

  19. Mineral Groups • Sulfates Group • Minerals made of SO4 bonded with other elements. • EXAMPLES: • Gypsum • Oxides Group • Minerals made with Oxygen bonded with other elements. • EXAMPLES: • Hematite & Ice

  20. Mineral Groups • Native Elements Group • Minerals that are pure elements (usually metals). • EXAMPLES: • Copper, Diamond, Graphite • Sulfides Group • Minerals made with Sulfur bonded with other elements. • EXAMPLES: • Pyrite

  21. Mineral Resources • Ores – useful metallic minerals that are mined at a profit. • EXAMPLES: Hematite (Iron), Sphalerite (Zinc), Galena (Lead), Cinnabar (Mercury). • Industrial rocks & minerals – useful nonmetallic minerals that are mined at a profit. • EXAMPLES: Fluorite, Sulfur, Halite (salt) • The amount of a mineral in a deposit must be concentrated several times it’s crustal percentage to be considered profitable.

  22. Mineral Resources • Gemstones – Crystal forms of minerals that posses beauty of such quality that command a price when cut & polished. • Precious gems – have beauty, durability, size, and rarity. • Diamond • Emerald (Beryl) • Ruby (Corundum) • Sapphire (Corundum)

  23. Mineral Resources • Semiprecious gems – only have one or two of the qualities of precious gems. • EXAMPLES: Amethyst , Topaz, Garnet, Zircon • Non-mineral gems – stones that have value, but are not minerals. • EXAMPLES: Coral, Amber, Pearl • Precious Metals – metallic minerals that have high value. • EXAMPLES: Gold, Silver, Platinum

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