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Tungsten Molybdenum Sapphires Treatments
作者:zean 时间:2014-05-06 16:56:10

Tungsten molybdenum sapphires may betreated by several methods to enhance and improve their clarity and color.It iscommon practice to heat natural sapphires to improve or enhance color. This isdone by heating the sapphires in furnaces to temperatures between 500 and 1800 °C for several hours, or by heating in anitrogen-deficient atmosphere oven for seven days or more. Upon heating, thestone becomes more blue in color, but loses some of the rutile inclusions(silk).

When high temperatures are used, the stoneloses all silk (inclusions) and it becomes clear under magnification. Theinclusions in natural stones are easily seen with a jeweler is loupe. Evidenceof sapphire and other gemstones being subjected to heating goes back at leastto Roman times. Un-heated natural stones are somewhat rare and will often besold accompanied by a certificate from an independent gemological laboratoryattesting to "no evidence of heat treatment".

Yogo sapphires sometimes do not need heattreating because their cornflower blue coloring is uniform and deep, they aregenerally free of the characteristic inclusions, and they have high uniformclarity. When Intergem Limited began marketing the Yogo in the 1980s as theworld is only guaranteed untreated sapphire, heat treatment was not commonlydisclosed; by 1982 the heat treatment became a major issue. At that time, 95%of all the world is sapphires were being heated to enhance their natural color.Intergem is marketing of guaranteed untreated Yogos set them against many inthe gem industry. This issue appeared as a front page story in the Wall StreetJournal on August 29, 1984 inan article by Bill Richards, Carats and Schticks: Sapphire Marketer Upsets TheGem Industry.

Diffusion treatments are used to addimpurities to the sapphire to enhance color. Typically beryllium is diffusedinto a sapphire under very high heat, just below the melting point of thesapphire. Initially (c. 2000) orange sapphires were created, although now theprocess has been advanced and many colors of sapphire are often treated withberyllium. The colored layer can be removed when stones chip or are repolishedor refaceted, depending on the depth of the impurity layer. Treatedpadparadschas may be very difficult to detect, and many stones are certified bygemological labs.


Details: www.chinatungsten.com
E-mail: info@chinatungsten.com

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