Tanzanite

Tanzanite is the blue-violet variety of the mineral zoisite and is one of the more recent discoveries in the world of gemstones. The stone became known in the 1960s in northern Tanzania and owes its name to the only country in which it is found in commercially significant quantities.

The commercially significant deposits lie in a small area near Merelani at the foot of Kilimanjaro. It is precisely this geographically very limited origin that makes tanzanite exceptional.

Its particular fascination lies in its pleochroism. Depending on the viewing direction, a tanzanite can show different hues, above all blue and violet, and in untreated material sometimes brownish or reddish nuances as well.

Many tanzanites are heated to reduce unwanted brown tones and bring out the characteristic blue to blue-violet. This heat treatment is customary in the trade.

Tiffany & Co. recognised the potential of the new gemstone early on, gave it the name “tanzanite” and made it internationally known from the late 1960s onwards.

With a Mohs hardness of about 6 to 7, tanzanite is suitable for jewellery, but it has distinct cleavage and should therefore be set and worn with care.

Fine tanzanites show an intense blue with a violet undertone, good transparency and high colour saturation. Particularly large, strongly coloured and clean stones are sought-after collector’s pieces.