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
Bauxite Minerals Limonite Minerals
Gibbsite Al(OH)3
Boehmite AlO(OH) Lepidocrocite FeO(OH)
Diaspore AlO(OH) Goethite FeO(OH)

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!