Gemstoes Notes from 3-12
Gemstoes Notes from 3-12 1108
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This 2 page Class Notes was uploaded by Caroline Bacevice on Thursday March 12, 2015. The Class Notes belongs to 1108 at Ohio State University taught by Loren Babcock in Spring2015. Since its upload, it has received 52 views. For similar materials see Gemstones in Earth Sciences at Ohio State University.
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Date Created: 03/12/15
Gemstones 312 Colors created Chemically The same impurities can color different gems differently o Chromium Cr3 I In corundum produces red ruby I In beryl produces emerald green emerald Charge transfer when electrons are swapped between elements through heating 0 Elements that oftenhave change transfer I Fe2Fe3 I Ti3 Ti4 I Mn2 Mn3 Mn4 o In sapphire heating transfers Fe2 and Ti4 to Fe3 and Ti3 producing a deep blue color Luminescence Emission of Visible light under the in uence of certain light rays 0 Fluorescence Luminescence under UV radiation I Caused by impurities in the crystal I Iron inhibits uorescence I Can be used to help differentiate natural from synthetic gems I Phosphorescence Luminescence that continues after irradiation has ceased Colors created Physically Phenomena Colors resulting from the interaction of light with physical structure of a stone 0 Iridescence Play of colors 0 Pleochroism Color change in different lights 0 Color Centers Structural imperfections in crystals causing selective absorption of light Iridescence Types 0 Orient rainbowlike colors in pearls o Opalescence Light diffraction in opal o Asterism Star effect inclusions in ruby or sapphire o Chatoyancy Cat s eye effect thin parallel inclusions o Adularescence Bluishwhite glow like a full moon moonstone o Labradoreescence Metallic hues labradorite Pleochroism Different colors that gems appear to have when viewed under different lights or in different directions 0 Caused by differing absorption of light rays in doubly refractive crystals Color Centers Imperfections in crystals cause absorption of light 0 Often due to radiation damage I Zircon containing uranium U blue I Zircon damaged by radioactive decay of U brownish red 0 Color Centers can be removed by heating I Zircon heat changes it to blue 0 Sunlight especially UV light can remove color centers I Amethyst exposed to sunlight will lose purple color Colors created Optically Colloidal Colors Caused by light re ecting from numerous tin inclusions in a mineral Example akes of mica in feldspar produce aventurine feldspar
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