Tanzanite Properties, Facts and Photos

What is Tanzanite?

Tanzanite is a rare, bluish-violet variety of the mineral zoisite discovered in northern Tanzania in 1967.

Tanzanite is mined in Merelani Hills, on the western slope of the Lelatema Mountains, approximately sixty kilometres from Mount Kilimanjaro. The deposit is just two kilometres wide by eight kilometres long.

Approximately 50,000 people in Merelani earn a living from tanzanite.

Tanzanite is an expensive gemstone often set with diamonds. Only a very limited amount of material is left available to mine.

The gemstone's bluish-violet hues come from impurities of vanadium.

Some tanzanite found at shallow depths naturally exhibits this highly sought-after colour, but it's incredibly rare. It's caused by geological warming, either by metamorphism, wildfires or because of thermal vents within close proximity to where it's found.

After being cleaned, most stones are heated to enhance their colour. This process can also remove yellow and brown tints that are often present when the stones are mined.

Tanzanite is heated for about thirty minutes at a maximum temperature of 400°C (approx' 734°F).
Unless stated otherwise, it's widely accepted that all tanzanite is heated. Tanzanite that hasn't been heated is far more valuable. Retailers should always know whether a gemstone has been heated, and if so, it must be disclosed.

The exact shade and depth of colour can vary greatly. Tanzanite gemstones with the deepest colour and good saturation command higher prices.

Colour is tanzanite's most important characteristic. Depending on the shade and level of saturation, it can be confused for blue topaz, iolite, aquamarine or sapphire.

Tanzanite is pleochroic which means it appears to be a different colour depending on the light and angle from which it's viewed. Under yellow light (which includes sunlight), it always appears more violet. 

Although correctly known as blue zoisite, the name was changed by the President and Chairman of the American jeweller Tiffany & Co. in 1968. The company introduced tanzanite to the world and said it could only be found in two places on Earth, Tanzania and Tiffany & Co.

Article Photos

The tanzanite crystals at the top of our article our courtesy of Stan Celestian.

The tanzanite in our second photo is courtesy of Géry Parent.

Both photos are clickable and redirect to the original image.