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Understanding Minerals: Identification Techniques and Properties in Earth Science

This guide covers essential methods for identifying and understanding minerals based on insights from Chapter 4 of the Earth Science book. Key concepts include recognition by color, luster, crystal system, and hardness, along with practical tests like streak, cleavage, and acid reactions. The importance of mineralogy and classification of minerals like silicates, carbonates, and oxides is discussed. It also emphasizes the significance of visual and physical properties in accurate identification, providing a valuable resource for students and enthusiasts of earth sciences.

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Understanding Minerals: Identification Techniques and Properties in Earth Science

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  1. How to Know Minerals read pages 46-57 Chapter 4 Earth Science Book restate & answer Topic Questions 1-9 practice the 30 lab mineral samples

  2. Topic 1: Page 47 Earth Textbook Rock-Forming Minerals * over 2000 minerals known * most are silicates (Si + O + metals) common minerals that make up the Earth’s crust * not always large crystals *mineralogy is the study of minerals and their properties

  3. Topic 2: Page 47-48 Earth Textbook Identification by Inspection *Color simple observations made by looking *Luster *Crystal System (shape)

  4. Topic 2: Page 47 Earth Textbook Color * first, most easily observed * least useful when identifying minerals 1. impurities change mineral’s colors 2. mineral’s colors are similar 3. colors change/react in air

  5. Topic 2: Page 47 Earth Textbook Luster * Metallic Luster * Nonmetallic Luster the way a mineral shines

  6. Topic 2: Page 47 Earth Textbook Metallic Luster *shines like polished metal *(galena, pyrite, chalcopyrite)

  7. Topic 2: Page 47-48 Earth Textbook Nonmetallic Luster *vitreous – shining glass (quartz) *pearly – like a pearl (mica) *resinous – like wax (sphalerite) *greasy, oily – (talc & graphite) *dull, earthy – (kaolinite, limonite) *brilliant, adamentine – (diamond)

  8. Topic 2: Page 47-48 Earth Textbook Crystal System (shape) *cubic – all 90º, all lengths equal *orthorhombic – all 90º, no lengths equal *tetragonal – all 90º, some lengths equal *triclinic – none @ 90º *monoclinic – some @ 90º *hexagonal – 3 axes @ 60º

  9. Topic 3: Page 48-50 Earth Textbook Identification by Simple Tests *Streak *Fracture or Cleavage *Hardness

  10. Topic 3: Page 48 Earth Textbook Streak * rub mineral on unglazed white tile metallic - streak dark as mineral the color of a mineral’s powder nonmetallic - streak colorless to light

  11. Topic 3: Page 49 Earth Textbook Cleavage 1 direction – micas, gypsum, talc 2 directions – feldspars, hornblende minerals split along flat surfaces 3 directions – galena, halite, calcite

  12. Topic 3: Page 49 Earth Textbook Fracture • concoidal fractures – shell-like fracture • fiberous or splintery – jagged and sharp minerals break along non-cleavage surfaces • uneven or irregular – rough surface

  13. Topic 3: Page 49-50 Earth Textbook Hardness *Mohs’ Hardness Scale – page 50 in text • minerals ranked on a scale of 1 to 10 minerals resistance to being scratched • need fingernail, copper, steel, glass, topaz • 1 softest (talc), 7 hardest common (quartz) and 10 is the hardest of all (diamond)

  14. Topic 4: Page 50 Earth Textbook Specific Gravity • specific gravity = mass of sample in air mass lost in water the ratio of the mass of a mineral to the mass of an equal volume of water • nonmetals - less than 4 • metals - above 5

  15. Topic 5: Page 51 Earth Textbook Acid Test *calcium carbonate fizzes in acid (HCl) *calcite is calcium carbonate, CaCo3 weak acid will release bubbles of CO2 *dolomite - CaMg(CO3) must be powdered *malachite & azurite are copper carbonates *limestone & marble calcite

  16. Topic 6: Page 51 Earth Textbook Special Properties • taste – halite is salty • magnetic - magnetite • double diffraction – calcite/Iceland par splits images into 2 • flourescence – glows under ultraviolet light, fluorite, sphalerite, willemite • phosphorescence – glows even after ultraviolet off

  17. Topic 7: Page 53-54 Earth Textbook Silicates • a) quartz • b) feldspars: orthoclase, plageoclase made with silica tetrahedrons (light colored) • c) micas: muscovite, biotite(black) • d) talc

  18. Topic 7: Page 54-55 Earth Textbook Ferromagnesian Silicates • e) amphiboles: horneblende • f) pyroxenes: augite silicates with iron and magnesium (darker) • g) olivine • h) garnets • i) kaolinite

  19. Topic 8: Page 55-56 Earth Textbook Carbonates *Calcium Carbonates • calcite(Iceland spar), dolomite made with carbonate group –CO3 *Copper Carbonates • malachite, azurite

  20. Topic 9: Page 56-57 Earth Textbook Oxides *Iron Oxides • hematite (reddish-brown streak) • limonite (yellow-brown streak) a metal combines with oxygen • magnetite *Aluminum Oxides • corundum • bauxite

  21. Topic 9: Page 56-57 Earth Textbook Sulfides • galena • pyrite a metal combines with sulfur • chalcopyrite • sphalerite

  22. How to Know Minerals read pages 46-57 Chapter 4 Earth Science Book restate & answer Topic Questions 1-9 practice the 30 lab mineral samples

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