I wonder how many gemologists would go the extra mile to identify an unknown colored stone. They would simply try using the basic tools and if they can't, they just give up. Also, how many even know what a taaffeite is. Sri Lanka, Burma, and Madagascar are treasure troves for the novice and experienced gemologists.
(via The Australian Gemmologist, Vo.23, No.2, April – June 2007)
Some time ago, a large mauve faceted stone was submitted for testing at GSL. This gemstone was among a suite of stones thought to be natural spinels.
When testing the stones, it was noted that the mauve faceted stone had a spot R.I reading of 1.71 and a specific gravity of 3.61, which are within the range of natural spinel. No visible inclusions were noted, and the stone showed no reaction when exposed to ultraviolet light.
However, further investigation showed that the stone showed a doubly refractive behavior on the polariscope and a uniaxial interference figure was noted. When precise refractive index reading were taken they were found to be 1.713 – 1.720 and the optic sign was uniaxial negative. Indeed, these data proved the large faceted mauve gemstone to be a rare taaffeite. This gemstone measured 12.8 x 9.5mm and weighing 5.20 carats.
Of the remainder of the group of spinels (?) submitted for gem testing, another pinkish oval gemstone, weighing 0.90 carat, also was identified as a taaffeite.
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