2. How do geochronologists use minerals? _________________

3. How many varieties of minerals have been identified? _________________

4. About how many common minerals are there? _________________

5. What’s the name given to electrically charged atoms? _________________

6. What 2 elements make up the mineral halite? _________________

7. What 2 elements make up the mineral quartz? _________________

8. What’s the tendency for minerals to break along flat planes called? _________________

9. What’s the way that minerals reflect light called? _________________

10. What are geologists who study the composition and origin of rocks called? _________________

11. In what layer of the Earth are diamonds formed? _________________

12. Where was gold discovered that started the great California Gold Rush? _________________

13. What are rocks that contain economically viable concentrations of minerals called? _________________

14. What group of minerals precipitates directly from sea or lake water? _________________

15. Give an example of a mineral that precipitates directly from a gas by sublimation. _________________

16. Give an example of a mineral formed by the biologic activity of sponges and corals. _________________

17. About what percentage of all minerals are the silicates? _________________