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Unveiling Earth's Treasures: Understanding Mineral Classes and Identification

Explore the fascinating world of minerals through their properties, classes, and identification methods. Learn about silicates, carbonates, and more. Discover how color, streak, luster, hardness, cleavage, fracture, density, and special properties like fluorescence and magnetism help identify minerals. Delve into the unique characteristics that make each mineral valuable and distinct.

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Unveiling Earth's Treasures: Understanding Mineral Classes and Identification

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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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