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Color Change Diaspore and Zultanite
Gemstones that change color under different lighting, such as alexandrite, are extremely rare, and most are quite valuable as well. So it was newsworthy in 2006 when a new color change gem came on the market called Zultanite. Even more intriguing, this new gem came from an unlikely source: Turkey.
|Color Change Diaspore
As things turned out, this gemstone was not a new discovery. Though the deposit in the foothills of the Anatolian mountains in southwest Turkey was a recent find, this mineral had been known since the early nineteenth century under the name Diaspore. It was first described in 1801 for an occurrence in the Ural mountains in Russia. The name is from the Greek, in reference to its decrepitation on heating.
Diaspore displays a subtle color change from a kiwi-like green in daylight to a champagne color in incandescent light, and a light purplish-pink under low intensity lighting such as candelight. The color change tends to be more pronounced in larger gems (over 5 carats). High quality diaspore tends to have excellent transparency with only minor inclusions.
Gemologically, diaspore is an aluminum oxide hydroxide by chemical composition and its crystals have an orthorhombic structure. Diaspore is reasonably hard at 6.5 to 7 on the Mohs scale, and it has a density or specific gravity of 3.30 to 3.39, similar to jadeite or peridot. Diaspore also has a relatively high refractive index at 1.702-1.750, ranking between tanzanite and spinel. Diaspore has perfect cleavage in one direction.
|Natural Color Change Diaspore from Turkey|
When Murat Akgun, a Turkish jeweler, acquired the rights to mine disaspore in Turkey, he introduced the Zultanite brand to evoke the Sultans of the Ottoman empire. More recently, the mine owner, Milenyum Mining, has marketed the material under the name of Csarite. To avoid the confusion of so many marketing names, we refer to this material by its gemological name, Diaspore. Turkish Diaspore would also be an appropriate name, since quantities of gem-quality material seem to be unique to that location.