|Tanzanite is the blue/purple variety of the mineral zoisite. (a calcium aluminium hydroxy silicate) It was discovered in the Mererani Hills of Manyara Region in Northern Tanzania in 1967, near the city of Arusha and Mount Kilimanjaro.|
This is the only known source in the world and it has been depleted over the years.
|Naturally-formed tanzanite is extremely rare.|
|Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet and burgundy depending on crystal orientation. Tanzanite can also appear different under various lighting conditions. The blues are more evident when subjected to fluorescent light and the violets can be seen when viewed under incandescent light.|
|Tanzanites are typically blue or violet-blue, but they can also be rare greenish and greenish-blue shades. Vanadium is the main coloring agent required to produce the rich blue-violet colors that are so highly prized. Tanzanite is a relatively new gemstone in the world of gemology and jewelry. Tanzanite is like all other gems in that small stones are more abundant than larger stones. Most faceted tanzanites are under five carats in weight. Stones over fifty carats are extremely rare and valuable. Since its discovery, tanzanite has sold for as little as $20 per carat and as much as $1,000 per carat or more, for gem-quality, finely coloured stones.|
That price may seem like a bargain in time, as tanzanite is a single-source gemstone and that source is expected to be mined out within the next 20 to 30 years.