Gemstones week of 1/26
Gemstones week of 1/26 1108
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This 2 page Class Notes was uploaded by Caroline Bacevice on Thursday January 29, 2015. The Class Notes belongs to 1108 at Ohio State University taught by Loren Babcock in Spring2015. Since its upload, it has received 61 views. For similar materials see Gemstones in Earth Sciences at Ohio State University.
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Date Created: 01/29/15
Gemstones Week of 126 Where gems form Igneous environments Sedimentary environments 0 Metamorphic environments Organisms Gems formed in igneous environments 0 Some gems crystallize from magma molten rock and bubbles of dissolved gases Pegmatite igneous Unusual igneous bodies containing large crystals 0 As magma cools water and rare elements become concentrated in the remaining melt because they do not get to incorporate in the early formed materials 0 When the last of the melt nally crystallizes there is enough water left to allow the last formed crystals to grow large in size and the crystals can incorporate rare elements Hydrothermal deposits igneousrelated Deposits of minerals cooled from superheated water water associated with magma bodies or heated groundwater Gems or metals crystallize from solution in cracks or other open spaces in rocks 0 Veins of minerals ll cracks Gems formed in the mantle igneous Some minerals are formed within the Earth and brought to the surface by volcanic activity Gems in sedimentary environments 0 Sediments or rocks formed by deposition of grains or participation of minerals from water Alluvial deposits 0 Formed from deposition and concentration of mineral grains weathered and eroded from preexisting rock Concentrations usually occur partly because of high density in stream beds and on beaches o Placer deposits Alluvial deposits of metals Ceylon Gem Gravels sedimentary deposits 0 IN Sri Lanka gems have been collected for hundreds of years from alluvial deposits 0 Gem weather from igneous or metamorphic rock and then become concentrated in auvia deposits 0 Similar gem gravels occur elsewhere Precipitation of gems in sedimentary deposits 0 Water near the earth s surface dissolves minerals o If the solution coos or water evaporated new minerals precipitate from solution Gems formed in metamorphic environments 0 Rock and its component mineral are changed by heat and pressure 0 Plate tectonics create metamorphic environments having high temperatures andor pressure 0 Subduction zones 0 Contact metamorphic zones next to cooing magma
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