EOSC 118 Lecture Notes - Lecture 20: Pegmatite, Gemstone, Tourmaline
15 Jul 2017
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Lesson 20 gem bearing pegmatites geology and geography. Intrusive igneous rocks that are texturally very course to gigantic in size: mineralogy directly tied to geochemistry, most characterized by base composition similar to granite but with significant enrichment in rare elements (be, li, cs, ta, nb, Y, f, rb, sn, ga, b: leads to formation of unusual minerals (i. e. beryl) List the rare elements that are commonly concentrated in fractionated granitic magma: be, li, ta, cs. Describe the global and local distribution of important gem-bearing pegmatite districts. Global: across globe but high quality gem bearing pegmatites are rarer, brazil (minas gerais), madagascar, russia, pakistan, us (pala district of. Local: none with gems, occur in young cordillera of western canada (bc, yukon, nwt) within. Granite: most common intrusive rock in earth"s continental crust, mottled pink, white, greay, black ornamental stone, coarse to medium grained, three main minerals: feldspar, quartz, mica (dark biotite or silvery muscovite)
