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Crystal Interfacial Angles

Crystal Interfacial Angles. Even when the crystals are different sizes, angles between equivalent faces are the same For different minerals, angles are different. 4. 4. 3. 3. 1. 1. 2. 2. Quartz. N. Lindsley-Griffin, 1999. Habit. Habit - distinctive shape of the way the mineral

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Crystal Interfacial Angles

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  1. Crystal Interfacial Angles • Even when the crystals are different sizes, angles between equivalent faces are the same • For different minerals, angles are different. 4 4 3 3 1 1 2 2 Quartz N. Lindsley-Griffin, 1999

  2. Habit Habit - distinctive shape of the way the mineral commonly (habitually) appears Concentric shells -- malachite N.Lindsley-Griffin, 1999

  3. Habit N. Lindsley-Griffin, 1998

  4. Crystal shape and Habit result from internal atomic structure N. Lindsley-Griffin, 1998

  5. Cleavage - tendency to break along planes of weak bonds N.Lindsley-Griffin, 1998

  6. Mica cleaves along planes of the weakest bonds N. Lindsley-Griffin, 1998

  7. Fracture describes how a mineral breaks on an irregular surface rather than along cleavage planes Types of fracture: Smooth Rough Splintery Conchoidal N. Lindsley-Griffin, 1998

  8. Hardness Hardness -- the resistance to being scratched Mohs scale measures relative hardness, the ability of one mineral to scratch another • Diamond 10 • Corundum 9 • Topaz 8 • Quartz 7 • Feldspar 6 Steel file (6.5) • Apatite 5 Glass (5.5- 6) • Fluorite 4 • Calcite 3 Copper penny (3.0) • Gypsum 2 Fingernail (2.5) • Talc 1 Mohs hardness scale: 1 = softest mineral; 10 = hardest © Houghton Mifflin 1998; Lindsley 2000

  9. The 10 minerals of Mohs relative hardness scale 4 Fluorite 3 Calcite 5 Apatite 1 Talc 2 Gypsum 10 Diamond 9 Corundum 6 Feldspar 7 Quartz 8 Topaz N. Lindsley-Griffin, 1999

  10. Luster Luster - the appearance of a mineral in reflected light Types of luster: Metallic Nonmetallic Pearly Vitreous Resinous Silky Dull Earthy Metallic luster of pyrite Earthy luster of limonite © Houghton Mifflin; N. Lindsley-Griffin, 1998.

  11. Metallic Luster is characteristic of ore minerals and others that contain metal cations. N. Lindsley-Griffin, 1998

  12. Resinous luster in sphalerite Pearly luster in talc N. Lindsley-Griffin, 1999

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