EARTHSC 1108 Lecture Notes - Lecture 17: Schist, Pegmatite, Diamond Cut
1 Dec 2016
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Document Summary
Gems from igneous rocks: peridot (olivine) Gems from pegmatites: tourmaline, topaz, spodumene (kunzite, hiddenite, zircon, beryl (emerald, aquamarine, morganite, chrysoberyl (alexandrite) Intrusive and extrusive: magma = molten rock material and hot, watery fluids rich in dissolved gases, extruded on the earth"s surface = lava, cooling and crystalizing below the surface = intrusive igneous rock. Cooled lava and ash: magma usually cooled fast, small crystals, lots of vugs (old gas bubbles) As si increases, so does na and k: as mg increases, so does fe and ca (but increases in opposite direction of si) Rocks with lots of gems in them are at either end of the spectrum (very high or very low. Could be derived from latin or arabic: formula: (mg,fe)2sio4. Unusual gem (only has 1 color, gem: found in igneous and metamorphic environments. Mineral structure of olivine (peridot: sio4 tetrahedra held together by mg2+ or fe2+ cations in between, formula: (mg,fe)2sio4, mg2+ and fe2+ are similar in size.
