1. Ionic radius is related to the valence of the ion - ions that have lost electrons (cations) are smaller than their neutral state, ions that have gained electrons (anions) are larger.

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3. If two cations are similar in ionic radius, one may substitute for another in a mineral structure. One of the more common substitutions is between Fe 2+ (~0.63 angstrom) and Mg 2+ (~0.57) and often a mineral contains a mixture of both Example is olivine - Fe 2 SiO 4 = fayalite; Mg 2 SiO 4 = forsterite; olivine = (Mg,Fe) 2 SiO 4 Ca 2+ and Na + can also substitute for each other in plagioclase feldspar.

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6. Silicates (SiO4)4-: The largest mineral group due to the fact that silicates are made up of the two most abundant elements in the crust: silicon and oxygen. The basic building block is the silica tetrahedra As oxygen : silicon ratio decreases, more and more silicon ions must share oxygen atoms in order to complete their tetrahedra.

8. Silicate mineralogy

9. 1.Isolated tetrahedra (monomer). O:Si = 4, olivine is the most common example (Fe,Mg) 2 SiO 4 no cleavage. Understand Solid solution of Fe-Mg 2.Single chain - silicate tetrahedra share oxygens with two other tetrahedra forming a long open ended chain. O:Si = 3, pyroxenes, 2 cleavages at ~90, Si 2 O 6 3.Double chain: two singles chains link together so each tetrahedra shares oxygens with three other tetrahedra. O:Si = 2.75, amphiboles, 2 cleavages at 60 and 120, Si 8 O 22

10. 4.Sheet silicates: silica tetrahedra form large sheets (link to three other tetrahedra) with all of the non-shared oxygens pointing in the same direction, Micas (biotite, muscovite):1 direction of cleavage. O:(Si+Al) = 2.5 5. Framework silicates: 3-d frameworks, all oxygens shared. O:Si+Al = 2. Common groups include quartz and feldspars (potassium feldspar/orthoclase, plagioclase). Most abundant minerals in the earth’s crust. (Solid solution in plagioclase) Can see increasing amount of SiO2 with increasing polymerization-also lower temperature.

12. Cabonates: calcite, dolomite Oxides: magnetite, hematite Sulfides, sulfates, halides, native elements

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16. How to ID minerals: Hardness: Moh’s scale Specific gravity Other properties (fizz, magnetic)

17. Moh’s scale

18. Color not always!

19. streak

20. Crystal habit

21. Cleavage-feldspars

22. Cleavage

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24. Concoidal fracture

25. Carbonates fizz