Tanzanite is the trade name of the mineral Zoisite. It formed around 585 million years ag but was found only recently, in 1967, in the shadows of the majestic Mount Kilimanjaro, in Tanzania; since that moment, it has become the second most famous blue gem after Sapphire.
The mineral zoisite naturally occurs in a wide range of colors that include colorless, gray, yellow, brown, pink, green, blue, and violet but the name “Tanzanite” is used for a specific color variety that ranges from blue, through violet, to violetish purple based on different lighting conditions.
Infact, untreated Tanzanite is a trichroic gemstone: it shows three colors, brown, blue and violet, concurrently. The heating, either naturally or artificially, minimizes bronze shades and so Tanzanite becomes dichroic and it accentuates to the maximum only blue and violet colors.
There isn’t identical results on each gem because this effect depends on the natural characteristics of each singular crystal. The finished color of the gemstone will vary depending on how its cut will reflect the light
Blue varieties, especially deep blue ones, are the rarest, most valuable and highly sought after.
A high transparency and the absence of inclusions accentuate its vivid colours, the hallmark of this gem.
The name of this Stone, Tanzanite, reflects also its limited geographic origin: the only existing field is located in Tanzania and occupies barely 20 square-kilometres. Because of its rarity and market demand, Tanzanite has been imitated in several ways but there are also a lot of test to distinguish the real one: the doubly refractive (blue, violet), the refractive index, the exam of the cut stone, through its crown facets and the pavilion cuts at the back of the stone, etc..
It is recommended not to subject the Tanzanite to drastic changes in temperature to avoid damaged.