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Mineral Criteria

Mineral Criteria. Inorganic: not made up of living things Naturally Occurring: exist in nature Crystalline Solid: regularly repeating crystalline structure Consistent Chemical Composition: consistent, no variety. Mineral Classes. Silicates: contain silicon (Si) and oxygen (O)

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Mineral Criteria

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  1. Mineral Criteria • Inorganic: not made up of living things • Naturally Occurring: exist in nature • Crystalline Solid: regularly repeating crystalline structure • Consistent Chemical Composition: consistent, no variety

  2. Mineral Classes • Silicates: contain silicon (Si) and oxygen (O) • Nonsilicates: do not contain silicon (Si) and oxygen (O), 6 major groups • Carbonates, Halides, Native elements, Oxides, Sulfates, Sulfides

  3. Mineral Identification • Color: easy to observe, minerals vary in color. • Many minerals are similar in color. • Small amounts of certain elements may greatly affect the color of a mineral. • Weathered surfaces may hide the color of minerals. • Examine freshly exposed surfaces.

  4. Gold

  5. Fluorite

  6. We’re going streaking! • Streak: color of the mineral in powdered form. • Rub a mineral against a piece of unglazed ceramic tile (streak plate). • The streak’s color may differ from the color of the mineral itself.

  7. My precious, precious. • Luster: light that is reflected from a mineral’s surface. • Metallic: reflects light similar to polished metal. • Nonmetallic: All other minerals. • Glassy, waxy, pearly, brilliant, and dull or earthy.

  8. Galena

  9. Hey, Mohs! Why I awtah… • Mohs hardness scale: standard scale against which the hardness of minerals is rated. (1-10) • 1 is soft, 10 is hard • The bonds between the atoms that make up a mineral’s internal structure determines the hardness of that mineral. • Test the hardness by scratching the minerals. • p. 111 Mohs Hardness Scale

  10. Hardness Scale

  11. Gypsum & Talc

  12. Diamond

  13. Cut! • Cleavage: tendency of a mineral to split along specific planes of weakness to form smooth, flat surfaces. • Break along flat surfaces that generally run parallel to planes of weakness in the crystal structure.

  14. Quartz

  15. Acanthite

  16. Time for a Break! • Fracture: break unevenly into pieces that have curved or irregular surfaces. • Uneven or irregular fracture: rough surface • Splintery or fibrous fracture: looks like a piece of broken wood. • Conchoidal fractures: curved surfaces.

  17. Asbestos

  18. Tiptopite (clear) Montgomeryite

  19. Not again! • Density: ratio of the mass to the volume of a substance. D=m/v • Depends on the kinds of atoms that the mineral has and depends on how closely the atoms are packed. • Heavy metals have larger densities. • Helps identifying heavier minerals easier.

  20. Special Properties • Fluorescence: glow under ultraviolet light. • Phosphorescence: continue to glow after ultraviolet light is removed. • Magnetism: attract metal, contain iron. • Radioactivity: nuclei of some atoms are unstable. • Results in nuclei decay over time.

  21. Magnetite

  22. Lights, Camera, Action! • Light rays bend as they pass through transparent minerals. • Double Refraction: Light rays are split into 2 parts as they enter the crystal. • Produces a double image.

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