A variety of the mineral zoisite, tanzanite is a blue-purple or purple blue color. In the cut and polished gems there are a kaleidoscope of colors including: royal blue, violet, indigo, lilac and periwinkle. It is one of the birthstones for December.
Tanzanite is the rare, precious gemstone variety of zoisite that occurs only in the foothills of Mt. Kilimanjaro in northern Tanzania, East Africa. It was discovered in 1967 and experts maintain that the chance of tanzanite occurring elsewhere in the world is one in a million. The supply of tanzanite is a finite one, making the gemstones of today, precious heirlooms of tomorrow.
Tanzanite is a polychromatic gem, meaning that depending on the angle from which you look at it, the stone may appear blue, purple or brownish-yellow. The first gems found were close to the surface and naturally heated in the ground, so they exhibited the characteristic blue-purple color. Currently the rough material found has not been heated in the earth and while on occasion there is a hint of the bluish color, it is mostly found as a brownish-yellow color. Today tanzanite is universally heat treated and produces a range of hues between bluish-purple to purplish-blue. Since heat treatment is universal, it has no effect on price, and finished gems are assumed to be heat treated. There is no structural or chemical change to the gem during heating which means that a tanzanite's color is natural and permanent.
The many hues of color that are found in tanzanites are all popular, as different hues appeal to different tastes. However gems with more intense color are considered more valuable. Larger stones tend to exhibit more intense color, fire and brilliance, and richly colored tanzanite typically commands the highest prices.
It is recommended that tanzanite should not be worn during activities that inflict excessive wear. It is ideally set as a dress ring, necklace or earrings. It should never placed in an ultrasonic bath for cleaning or brought into contact with acids.
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Photos courtesy of: A.Balthrop/Akanni