BAESI: Minerals November 19, 2011 Ellen Metzger
Bay Area Earth Science Institute Since 1990 Web Site: www.baesi.org
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Acknowledgements The BAESI Saturday workshop program is made
possible by a grant from Chevron. Geologic maps of California supplied by the
Northern California Geological Society and the American Association of Petroleum Geologists Foundation.
What is a Mineral?
A mineral is a naturally-occurring, inorganicsolid with a definite (but generally not fixed)chemical composition and an orderlyinternal arrangement of atoms (crystalline).
Examples of chemical formulas for minerals:
Quartz: SiO2
Pyrite: FeS2
Both are crystalline
http://skywalker.cochise.edu/wellerr/VGM/mineral-hall.htm
Virtual Geology Museum at Cochise College – Copyright-free phtos
"Walking into either of these caves is like stepping into a gigantic geode," said Richard D. Fisher, an American consultant with the mining company to develop the discoveries as tourist attractions. Fisher said that most people can endure only a few minutes in the caves due to their high temperatures.
Physical properties used to identify minerals
Color Streak Luster Hardness Cleavage/fracture Specific gravity (“heft’) Reaction with dilute HCl (or vinegar) Magnetism Crystal habit or form
Two Forms of Hematite: Same Streak
http://www.li-edu.com/hematite.gif
http://www.belmont.sd62.bc.ca/teacher/geology12/photos/minerals/streak_hematite.jpg
Moh’s Scale of Hardness1 = Talc 2 = Gypsum 3 = Calcite 4 = Fluorite 5 = Apatite6 = Orthoclase 7 = Quartz 8 = Topaz 9 = Corundum 10 = Diamond
Hardness of everyday objectsFingernail: 2.5Penny ~ 3.5Glass and a steel nail: 5.5 and
Examples of Cleavage
http://upload.wikimedia.org/wikipedia/commons/9/93/Mineral-cleavage.gif
Look for signs of breakage: “steps” on mineral surfaces
Fracture: Irregular Breakage
http://geophysics.ou.edu/geol1114/notes/minerals/conchoidal.jpg
Quartz has conchoidal (curving fracture)