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| A touchstone design: Velvet Blue Daiquri Ring: Tanzanite and White Gold |
There are only two known deposits of tanzanite in the world. A small and uneconomic deposit has been found in Kenya. While the main and only economic deposit islocated in the Merelani Hills near Ausha, Tanzania. Estimates vary, but in all likelihood with consumption continuing at it current levels, the Merelani Hills deposits of Tanzania will be completely depleted within 20 years.
While Tanzanite is a relatively recent discovery, similar minerals were discovered almost two hundred years ago in the Austrian Alps. Natural tanzanite is in fact a rather dull yellow-brown colour, and most tanzanite has been heat treated to produce the striking violet-blue colour. When heated to 400-500 degrees C, the natural yellow and brown tints vanish and an amazing blue develops. The colour of the highest quality tanzanite is described at cobalt ultramarine. The most sought after colour is a strongly saturated blue displays a purplish almost amethyst undertone.
Tanzanite while a beautiful stone, has a low hardness (6.5-7) compared to other gemstones, and should be worn with care in all but designs that prevent the gem from being knocked or scratched. Pieces such as earrings and pendants are great options over everyday rings . With care a master craftsman can create a ring for daily wear that does justice to the gem and protects is within certain limitations of design.
Tanzanite exhibits three different colours when viewed along each of the three major axis (x, y & z). This pleochroism from very strong violet blue to brown, means the stone appears different colours, when viewed from different angles. In daylight the appearance of the stone is more blue, while under artificial light a more Amethyst violet colour is seen in the same stone. As a transparent Type 1 gemstone, most are eye clean except in very large pieces.
Large tanzanites are not uncommon, with the largest recorded cut stone to date being 731.81 carats. One of the most famous is the 242carat “Queen of Kilimanjaro” currently on display in the Gallery of Gold and Gems at the Royal Ontario Museum in Toronto, Ontario, Canada.
During the month of December, purchase any tanzanite on our website www.touchstonegems.co.za and get 20% off the purchase price. This offer is valid until 24th December 2010.
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