Скачать или смотреть 2.02 Carat Unmounted Oval Shaped Tanzanite A Quality

About Tanzanite:
Introduction:
Tanzanite, the Gemstone of the 20th Century was first discovered by Massai tribesmen in the 1960s in Tanzania. The fact is Tanzanite is actually a form of Zoisite and only through fire (heat treatment) can its almost unrivalled natural beauty be revealed. Sought to be the fourth precious gemstone by Tiffany & Co, with its lush blue and purple colours, Tanzanite can be found in showcases alongside rubies, sapphires and emeralds. It is also listed as the birthstone for December by the American Gem Society (AGS).
Colour is often considered the most important criteria when grading Tanzanite gemstones. Tanzanite can display different colours from one angle to another. Although it is actually a three-coloured stone that shows flashes of purple and red, Tanzanites predominant colour is a deep royal blue. The less brown or gray present and the more saturated the colour (but not to the point which its so dark that the Tanzanite looks more like a black onyx), the more valuable the Tanzanite gemstone. Even though face-up hues ranging from blue to violetish blue command the highest prices, the best Tanzanite colour for you depends on your purpose for the purchase, your budget and your personal preference and personality. Please note that Tanzanite is almost always heat treated to enhance its colour and a Tanzanite gemstone which appears blue or violet in daylight or fluorescent lighting may look purple under incandescent light.
Clarity is also important in a Tanzanite grading report. Classified as type I by Gemological Institute of America (GIA), Tanzanite should be ideally eye-clean (free of flaws visible to the unaided eye). High quality Tanzanite gemstones are graded lightly included or above according to the linear clarity scale developed by American Gemological Laboratories (AGL). Please note that the diamond clarity grading system (VVS, VS, SI and I) developed by GIA is normally not used on coloured gemstone grading.
Cut also contributes to the value of Tanzanite gemstones because it affects their colour and clarity as well as their brilliance. Some of the popular cut shapes for Tanzanite are oval, cushion, rectangular, trillion and pear and almost all Tanzanite are faceted. Please note that unlike diamonds which are cut based on strict mathematical parameters, most coloured stones are cut for weigh retention and a Very Good grade is very difficult to obtain.