2. ROCK vs. MINERAL n ROCK n Mixture n Can be separated by physical means n MINERAL n Pure substance n Has specific formula n Cannot be separated by physical means

4. MINERAL FORMATION Geology classes

5. FROM A MELT n Form from lava or magma n most common method n Usually forms large crystals n example: quartz, gemstones

6. From a solution nEnEvaporation uHuHalite, gypsum nUnUsually soft minerals nPnPrecipitation from saturated solution uCuCalcite, barite

7. From Heat and Pressure nMnMainly in metamorphic rocks nCnCreates very hard minerals ugugarnet ududiamonds

8. From Hydrothermal n Hot watery solutions u Rain water percolates and is heated by interior of earth u Chrysocolla, azurite, gold

9. Classification of Minerals n Nearly 4000 minerals have been identified on Earth F Only 8 elements that make up over 98% of the Earth’s crust- THE BIG 8

10. ABUNDANCE OF ELEMENTS ELEMENT% BY WEIGHT OXYGEN46.6% SILICON27.7% ALUMINUM8.1% IRON5.0% CALCIUM3.6% SODIUM2.8% POTASSIUM2.6% MAGNESIUM2.1%

11. The silicate (SiO 4 ) -4 molecule (tetrahedron) n Wants to join with positive ions u Fe, Mg, K, Na, Al, Ca n Or joins with other tetrahedron (covalent) n Si joins tough with O = hard minerals (mostly)

12. Positive ions may substitute for each other n If same charge and same size u Ca and K u Fe and Mg n Use commas in formula to indicate substitution n olivine

13. Silicate structures- most common group of minerals Less space= harder

14. Olivine u Single tetrahedron u No cleavage

15. Pyroxene family- single chain augite2-directional clevage

16. AMPHIBOLE FAMILY- double chain Hornblende crystals- 2 cleavage

17. MICA FAMILY n Sheet silicate- one directional cleavage u MUSCOVITE u BIOTITE

18. Feldspar family- most common group Potassium feldspar (orthoclase)

19. Feldspar family Plagioclase feldspar

20. Quartz- Si and O only!!

21. Impurities n Can change color n But not chemistry!!

22. NON-SILICATES n Carbonates (CO 3 ) u Calcite, dolomite n Sulfates (SO 4 ) u gypsum n Halides (halogens) u fluorite n Native minerals u elements

23. FORMULAS n Subscripts n Parentheses n Opal n commas