Zultanite: A Color Changing Stone
Zultanite gemstones, rough and crystal form lighting

Zultanite is a color change gemstone that is similar to alexandrite. Zultanite is a trade name for gem quality diaspore. The term was introduced by the owner of the only known deposit of zultanite.

The color of zultanite is hard to describe as it changes color under different light sources and when viewing from a different angle. Most zultanite however displays earthy hues that change from yellow-green or greenish colors in sunlight to pinkish-purple or reddish colors under artificial light.

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.

Zultanite has a fairly high hardness of 6.5 to 7, falling short of the other well-known color change gemstone alexandrite. It also has perfect cleavage, this means that it can more easily split when you are not careful while wearing it. Despite this it is suitable for jewelry, but you will have to be careful with it.

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.

Zultanite has only a single known source in Mugla, Turkey deep in the Anatolian Mountains. Diaspore crystals have been found in other countries, but so far no other gem quality deposit has been found.

High quality zultanite up to 1 carat that is eye clean and has an excellent cut will sell for roughly $200 per carat.

See also: 
Thunderegg: Ordinary Rocks With Crystal Surprise Inside!
Chrysoberyl: One of the World's Most Exotic and Expensive Gems