|Diaspore or Zultanite?
Over the centuries that man has been scouring the earth for valuable minerals, one would think that all the different types of gemstones had already been discovered. However, new ones seem to be found on a fairly regular basis and some of these have become very important with regard to the international gemstone and jewelry market.
Tanzanite was discovered as recently as the 1960s and tsavorite garnet in the 1970s, both in East Africa. Chrome diopside was first found in Russia in the 1980s, and Paraiba tourmaline from Brazil first appeared on the market in the early 1990s. More recently there has been a lot of publicity surrounding andesine labradorite, though it turned out to be not 'andesine', but color-enhanced labradorite.
The latest new find in the gemstone world is a delicately-colored stone with interesting color-change properties being promoted under the name zultanite. Mined from a single deposit in the mountains of Central Turkey, the name zultanite is a brand name introduced by the man with mining rights to the deposit, Murat Akgun. The name is assumed to reference the sultans who ruled the Ottoman Empire.
The name zultanite may be new, but this particular mineral has been known since 1801 when it was first discovered in the Ural Mountains of Russia. Its gemological name is diaspore, and it is hydrated aluminum oxide colored by manganese. It was first faceted as a gemstone in the 1980s, but was not commercialy mined until recently.
Diaspore has reasonably good gemstone characteristics. It has a hardness of 6.5 to 7 on the Mohs scale, comparable to peridot and tanzanite. It has a refractive index of 1.702 to 1.750, which lies between that of tanzanite and spinel. Diaspore has perfect cleavage in one direction, making it a challenge to cut.
Gems that change color under different lighting are rare and diapsore is attracting buyers who are drawn to this unique quality. Under natural or fluorescent light, diapsore has a kiwi green color, with flashes of yellow. Under incandescent lighting, this shifts to a champagne color, and when exposed to subdued lighting, such as candlelight, diaspore has a pinkish color. The larger the stone, the more pronounced the color change effect.
Diaspore deposits have now been found in a number of locations around the world, including Arizona and Pennsylvania in the USA, New Zealand, Brazil, Argentina, Russia, the UK and China. However, to date, the only gem-quality material has been mined in Turkey.
- First Published: April-22-2008
- Last Updated: June-12-2014
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