TANZANITE
BUYING GUIDE

By Richard W. Hughes
 

Introduction/Name

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.

Lighting

Tanzanite is extremely light sensitive, with incandescent lighting tending to shift its color to the violet side. The best pieces show an intense blue under any light.

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.

Prices

Tanzanite prices probably fluctuate more than any other gem, largely due irregular production at the mines. For extremely fine stones of less than 50 cts., prices sometimes top $1000/ct. at retail.

Stone Sizes

Tanzanites sometimes occur in extremely large sizes, with faceted gems of hundreds of carats in existence. The most popular sizes for jewelry use are those below 20 cts.

Sources

The only locality for tanzanite is Merelani in Tanzania.

Enhancements

Virtually all gem tanzanite of a blue color has been heat-treated to enhance the color.

Imitations

Tanzanite has never been synthesized, but a number of imitations exist. The most common is blue-violet glass. A synthetic fosterite has also been used as an imitation.

Properties of Tanzanite