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Black gold is a type of gold used in jewelry. [16] [17] Black-colored gold can be produced by various methods: Patination by applying sulfur- and oxygen-containing compounds. Plasma-assisted chemical vapor deposition process involving amorphous carbon; Controlled oxidation of gold containing chromium or cobalt (e.g. 75% gold, 25% cobalt [4]).
Analyzing gold using XRF spectrometers gives the purity of gold, up to 10-12 microns and hence it gives the analysis of coating only. Using this technique, the precise percentage or karat (of karat ) in a solid piece of jewelry can be determined in 30 seconds.
For example, a gold alloy of 127 ⁄ 128 fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold. The carat fractional system is increasingly being complemented or superseded by the millesimal system, described above for bullion, though jewelry generally tends to still use the carat system.
The BIS system of hallmarking of gold jewellery began in April 2000. The standard specifications governing this system are IS 1417 (grades of gold and gold alloys, jewellery/artefacts), IS 1418 (assaying of gold in gold bullion, gold alloys and gold jewellery/artefacts), IS 2790 (guidelines for manufacture of 14, 18 and 22 carat gold alloys only ), IS 3095 (gold solders for use in manufacture ...
The Wittelsbach diamond, before being recut by Graff. The original Wittelsbach Diamond, also known as Der Blaue Wittelsbacher, [3] was a 35.56-carat (7.112 g) fancy, deep, greyish-blue diamond with VS2 clarity that had been part of both the Austrian and the Bavarian Crown jewels. [4] Its colour and clarity had been compared to the Hope Diamond ...
The Comtesse de Vendôme is a diamond necklace composed of 116 diamonds, [1] including a centerpiece 125-carat diamond, [2] and an estimated value of approximately 31 million dollars (in 2004). [3] The necklace was stolen from the Tokyo jewelry boutique Le Supre-Diamant Couture de Maki on March 5, 2004 by thieves who are believed to belong to ...
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