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Understanding Non-Silicate Minerals: Characteristics and Structure

Learn about important hematite-corundum, ilmenite, and spinel minerals and their crystal structures. Explore their properties and applications in different geological contexts.

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Understanding Non-Silicate Minerals: Characteristics and Structure

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  1. Important Non-Silicates

  2. Hematite-Corundum • Ilmenite FeTiO3 is similar

  3. Halite and Galena

  4. Pyrite

  5. Diamond

  6. Diamond

  7. Sphalerite

  8. Chalcopyrite

  9. Halite and Calcite

  10. Calcite

  11. Fluorite • Uraninite UO2 is isostructural

  12. Goethite

  13. Goethite

  14. Goethite

  15. Lepidocrocite

  16. Lepidocrocite

  17. Bauxite and Limonite

  18. Perovskite

  19. Perovskite in the Mantle • Perovskite is CaTiO3 • Enstatite (Mg Pyroxene) = MgSiO3 • Can collapse to perovskite structure at high pressure

  20. Rutile

  21. Rutile

  22. Rutile • Cassiterite SnO2 is isostructural

  23. The Spinels • AB2O4 • A is divalent, B is trivalent • Oxygens in cubic close-packed structure • In a close-packed structure, there is one octahedral site for every oxygen and two tetrahedral • Ideally B occupies half of octahedral sites and A occupies 1/8 of tetrahedral sites

  24. Normal and Inverse Spinels • In normal spinels, B (trivalent) occupies octahedral sites and A (divalent) occupies tetrahedral sites • In inverse spinels, A (divalent) occupies octahedral sites and B (trivalent) occupies tetrahedral sites • In real spinels there is a lot of crossover

  25. Important Spinels • Spinel (normal) MgAl2O4 • Hercynite (normal) FeAl2O4 • Magnetite (inverse) Fe++Fe+++2O4 • Chromite (inverse) FeCr2O4 • Ulvospinel (inverse) Fe2TiO4 • Franklinite (inverse) ZnFe+++2O4 • Maghemite (inverse) Fe2O3

  26. Spinel

  27. Spinel

  28. Spinel

  29. Spinel

  30. Spinel in the Mantle • Spinel = AB2O4 • Forsterite (Mg olivine) = Mg2SiO4 • Can collapse to SiMg2O4 at high pressure • Si in octahedral sites, not tetrahedral!

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