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by: Mr. Jasmin Ratke


Mr. Jasmin Ratke
GPA 3.76

Mark Helper

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Mark Helper
Class Notes
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This 3 page Class Notes was uploaded by Mr. Jasmin Ratke on Sunday September 6, 2015. The Class Notes belongs to GEO 347K at University of Texas at Austin taught by Mark Helper in Fall. Since its upload, it has received 50 views. For similar materials see /class/181657/geo-347k-university-of-texas-at-austin in Geology at University of Texas at Austin.




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Date Created: 09/06/15
M Helper GEO 347K Spring 3995 Notes on Gemstone Treatments and E 39 Treatment of gems to modify colors an old practice Pick up Pliny s Natural History lst Century AD and read about use of dyes to make quartz look like emerald redden stones use of foil backings heat and applying thin coats of paint to alter gems appearance Many of these ancient practices particularly the applications of oils and dyes survive to the modem day In Pliny s day use of these techniques constituted fraud but today some are accepted as commonplace oiling of emeralds heating of aquamarine With the passage of the ages and the development of new technologies people tinkering with alteration of color in gemstones have developed an impressive list of techniques In the last 40 years with the incredible growth in technologies the amount of experimentation has exploded so that today the treatment of gems is much more prevalent than in the past This has occurred so rapidly that the ethical issues surrounding many treatment techniques are still hotly debated with the gem and jewelry industry Brief outline of prevalent treatment techniques given below Enhancement and Alteration of Color in Gemstones I Introduction A Enhancement vs Alteration semantic diiTerences Any maninduced change of color or clarity B Color electrons are absorbers of light We see what s left over Color of light being absorbed depends on the con guration of the electron present 1 Electrons that produce color are found in two different con gurations a First row transition metals present as impurities b Color Centers II Enhancement Techniques A Dying Oiling Oldest of all practices Pliny describes dyes applications to imitate ruby wine emerald salts of copper used with the urine of an quotuncorrupted youthquot B Coatings Foil backing color tint applied Common technique before advent of pavilion faceting to improve brilliance Not so common today except in inexpensive imitations C Heat Treatment 1 Ancient Practices UI V Carnelian Brown or yellow to Red Aquamarine remove greenish hue Amethyst to Citrine Blue to colorless sapphire Zircon hyacinth Brown topaz to pink Modern Practices Ruby Colorless Orange Yellow Darker blue sapphire Tanzanite Temperature Range 300 2000 0 C Practice bury in substance sand lime iron lings Alumina powder charcoal so heat penetrates slowly cool slowly Effects a Change valence of coloring element change color lighten darken Brownish Red Ruby gt Red Ruby Amethyst gt Citrine Brown Zoisite gt Tanzanite Pale Yellow Sapphire gt Golden Sapphire b Destroy color centers fading change of color Smokey Quartz gt Colorless Brown Topaz gt Pink Topaz c Melt mineral inclusions clarity darken Silky Whitish Blue Sapphire gt Blue Sapphire d Change hydration state limonite to hematite Brown Chalcedony gt Camelian Tigers Eye gt Hawks Eye e Precipitate new mineral asterism Sapphire gt Star Sapphire f Impurity Diffusion add color Colorless Sapphire Fe and Ti paste gt Blue Sapphire D Irradiation Began with Curries who noted the glass tubes in which they stored their radium turned bluish Present day desertamethyst glass Fraciose Bordas buried sapphire in radium salt and noted change from colorless to yellow and blue to green By 1909 use of Ra to turn colorless diamonds green had been noted 1957 irradiation and heating to form blue topaz noted By 1974 was being practiced in earnest Serendipitous discovery Topaz mixed in with a lot of quartz by mistake Were studying smokey quartz colorless quartz transition Pink Sapphire gt Padparascha Colorless Diamond gt Fancy Diamond Rock Crystal gt Smokey Quartz Citrine gt Amethyst Kunzite gt Hiddenite Colorless Topaz gt yellow orange brown or blue Topaz Goshenite gt Golden Beryl All occur naturally in these colors Natural radiation by decay of trace amounts of U Th and K and bombardment by cosmic rays Cummulative processs over long time periods Pegmatites or Krich rocks are particularly abundant sources of radiation Why isn t all quartz smokey etc May have been heated May have formed in non radioactive environment


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