One of the most exciting gem discoveries of the twentieth century is tanzanite, which was first seen in Tanzania in 1967. It was publicized by Tiffany & Co. It has a vibrant blue to blue violet color and can easily be mistaken for the finest sapphire.

Tanzanite, Tanzania (Photo by ICA/Bart Curren)

If you are looking at a tanzanite it is critical to view it under different lighting conditions. In daylight tanzanite will display the most blue, incandescent light will bring out the violet color. Generally those stones that are brilliant blue with minimal violet, even in incandescent light, will command the highest price. If you prefer the violetish shades you will pay less.

Before the incredible blue shade is created by heat, resulting in tanzanite, the zoisite is a greenish to brownish color which is extremely trichroic. There is some zoisite that has been naturally heated by the sun to turn the material to tanzanite, but most is gently heated before cutting.

(Green chrome zoisite. Photo by ICA/Bart Curren)

Tanzanite is generally easy to find without eye visible inclusions. The first tanzanite available was only available in small stones. Today large stones are available even in ten carat or more sizes. Prices for small stones under three carats still can be found in the moderate price per carat range. Large fine gems will be in the expensive price per carat range.

Tanzanite is a fragile stone. It is brittle and if it is to be worn as ring stone it should be set in a mounting that will protect the stone. It may scratch and abrade at the facet junctions rather easily. It should never be put into an ultrasonic cleaner. Other zoisite colors are not of commercial importance as gemstones.