Introduction: Tanzanite is the name given to the rich blue-violet variety of the epidote-group mineral, zoisite. The gem was first discovered in Tanzania in 1967 and was named after its country of its origin, Tanzania, by the famous New York jeweler, Louis Comfort Tiffany.
Color: Tanzanite has what many would consider the finest blue hue in the world of gemstones, a color which often leaves even the finest sapphires lacking. The gem is strongly trichroic. A chromium-colored green tanzanite is also found in Tanzania.
Clarity: In terms of clarity, tanzanite does occur in reasonably clean crystals. Thus when buying, the standard is eye-clean stones.
Cut: In the market, tanzanites are found in a variety of shapes and cutting styles. Ovals and cushions are the most common, but rounds are also seen, as are other shapes, including emerald cuts, trillions, etc. Cabochon-cut tanzanites are not often seen.
Moh’s hardness: 6.5 – 7
Specific Gravity: 3.35
Refractive Index: 1.691 -1.700
Countries of Origin: Tanzanite is found in the East African state of Tanzania.
History, Literature and Lore: Previously known as zoisite, the stone was first described in 1905, with a pink variety, thulite, from Norway, often used as an ornamental stone in carbochons and carvings.A uniquely beautiful tanzanite, “The Midnight Blue,” of 122.7 carats, is displayed in the Natural History Museum in Washington, D.C.
How To Choose: Tanzanite is tri-chroic, meaning it has three color directions. If properly oriented the fine, pure blue color shows from the top with the violet only visible from the sides. In an attempt to have higher recovery from the rough, the producers cut them to mix the blue and violet, and market that as the desired color. The finest examples should be that pure, rich blue without violet. The stone can be fragile and ultrasonic cleaning should be avoided. Because of limited mining, the price of tanzanite remains very high– especially the higher quality, larger stones. We at INTA Gems will be more than happy to help you choose the best stone for you!