Zultanite, Csarite or Diaspore?
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.
Color Change Diaspore Gemstone
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 names, Zultanite, Csarite and Color Change Diaspore. Gemologically, all three refer to the same material, a gem-quality variety of diaspore that exhibits a rare color-change optical phenomenon. It is mined from a single deposit in the mountains of Central Turkey, the names zultanite and Csarite are marketing or brand names, rather than official gemstone trade names. These names were introduced by either the company or the man with mining rights to the deposits, located in Murat Akgun. The name 'Zultanite' is assumed to reference the sultans who once ruled the Ottoman Empire.
The names Zultanite and Csarite may be relatively 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 form of hydrated aluminum oxide colored by manganese. It was first faceted as a gemstone in the 1980s, but it wasn't commercially mined until more 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 color-change diaspore 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 degree of color change can vary from stone to stone, but most exhibit subtle change. Typically, the larger the stone, the more pronounced the color change effect will be. Large gemstones with very strong color-change often sell for excess of hundred dollars per carat as they are extremely rare.
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 United Kingdom and China. However, to date, the only gem-quality, facetable material has been mined in Turkey.