Spotlight on the gem world: Three unique red diamonds.Natural fancy red colours are the rarest and m

Spotlight on the gem world: Three unique red diamonds.Natural fancy red colours are the rarest and most expensive diamonds of all. Only a very few stones exist worldwide, and laboratory certificates grading the hue as pure red, without another colour modifier (such as purplish), are almost unheard of. Pink diamonds are also reds, but with low colour saturation. At the opening of this year’s Argyle mine pink diamond tender in Sydney, Rio Tinto unveiled these three luscious rocks. Out of the millions of carats mined last year, only 64 stones made it into the fancy colour tender, since most of the mine’s production consists of small yellow/brown stones, cut in India and marketed as cognac and champagne diamonds. Many moons ago we did a post on Argyle pink diamonds, whose deep colours are only found at this mine, it’s available at http://tinyurl.com/lfc4cxw. Since the mine (located in the Kimberleys in Western Australia) opened in 1983, only six stones from Argyle have been certified fancy red by the Gemmological Institute of America, and half of them are now for sale in the same tender. The piece de resistance is a 1.56 round brilliant cut fancy red, named the Argyle Phoenix in honour of the recent opening of underground operations after a several year refit. The collection also includes 58 pink/purple and three blue diamonds, with the largest stone being a 3.02 carat orangey-pink, called the Argyle Imperial. The red stones are expected to fetch well upwards of a million dollars a carat when the tender closes in October after visits to Sydney, Perth, New York, Hong Kong and Tokyo . The last red stone sold for 1 Million/ct in 2008 but prices of fancy colour diamonds at auction have rocketed since the beginning of the financial crisis.The diamonds were all cut and polished by Rio Tinto in Perth, where their skilled diamantaires have developed great expertise in combining high quality cutting while extracting the best colour and weight out of the rough stones. The colour is due to colour centres that absorb light. These are induced by pressure straining the crystal structure of the stones. Pink and brown diamonds are coloured by the same process, and one frequently sees pink and brown lines of colour together aligned along crystal axes when examining these stones with a hand lens. These are called dislocation planes, and the colour reflects the pressures and strains deep in the Earth that affected the Kimberleys back in deep time.LozImage credit: AFPwww.argylepinkdiamonds.com.auhttp://www.diamonds.net/news/NewsItem.aspx?tc_dailyemail=1&ArticleID=43124http://www.perthnow.com.au/business/rare-argyle-diamonds-up-for-sale/story-fnhocr4x-1226645526697http://www.heraldsun.com.au/news/rio-unveils-rare-fancy-red-diamonds-at-annual-argyle-tender/story-e6frf7jo-1226645350205 -- source link

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