Tanzanite is part of the zoisite class of minerals. It was named by Abraham Werner in 1805 for Baron von Zois after Werner discovered the mineral zoisite for the first time in the Alps. Green and brown zoisite should be identified in commerce as "green and brown zoisite," not as "green tanzanite."
Tanzanite, Tanzania (22.85 ct)
Color: blue-violet, blue, violet
Hardness: 8 (this stone is difficult to grind because of its cleavage)
Most important deposits: Tanzania
Tanzanite is named for the country of its discovery, Tanzania, where it was discovered in 1967 in the Merelani Mountains in the Lelatema District, and this region is the sole place where it is mined to date.
Through heating, the color can be changed from brown-blue to blue; nature has already done this in many cases for tanzanites that occur in depths below 700 meters. Unfortunately such depths require working with explosives, which makes it quite challenging to secure larger raw stones of tanzanite, which easily cleaves.
Tanzanite is colored blue by the element vanadium; interestingly, vanadium is the source for green, not blue, in many other minerals. Tanzanite is among the most difficult to grind gemstones.
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