1. Chemical Basis for Formation of Ores How do we get a lot of one element in a small place? Ore: a body of rock with a relatively high concentration of an element

2. Magmatic Concentration: Mainly for abundant metals Eutectic Diagrams

3. Sublimation Mainly just Sulfur

4. Evaporation Highly soluble salts: NaCl, KCl, NaNO 3

5. Weathering: mechanical concentration Rock breaks down, is transported by water, and deposited all in one place. Example: gold.

6. Weathering: Residual Concentration Resistance to weathering- single compound left in one place. Al 2 O 3 deposits formed this way.

7. Bacterial Action: Insoluble Sulfide Ores Sulfate reducing bacteria: SO 4 2- + carbohydrates (CH 2 O) + 2 H +  H 2 S + 2 CO 2 + 2 H 2 O Pb 2+ + H 2 S  PbS + 2 H +