Tanzanite (Tan•zan•ite ): Tanzanite, possessing what is considered to be the optimum blue of any gemstone, can leave even the best sapphires lacking. However, most Tanzanite occurs naturally as a transparent brown or green crystal, colored by vanadium. This material is routinely heat treated to temperatures of approximately 500 degrees, turning it light to dark violet, blue and bluish purple.

Tanzanite displays strong trichroism, which means it displays three different colors from different directions: blue from some, purple from others, you may also see flashes of red, green, yellow, orange, or brown. Tanzanite is also extremely sensitive to different light sources, changing color to the violet end of its spectrum under incandescent light: better quality specimens will remain an intense blue under all light. Clarity in Tanzanite is generally clean to standard eye-clean gems.

Because it is found in quite large sizes, gems of hundreds of carats are in existence, Tanzanite can be cut into almost all shapes. The most popular sizes are less than 20 carats in ovals and cushion cuts; rounds are also popular, as are other cuts such as emerald and trillion. Tanzanite is a variety of Zoisite, a hydrated calcium aluminum silicate, possessing a hardness of 6.5 to 7 on the Moh's hardness scale with a perfect cleavage. The cleavage can make Tanzanite brittle so it should be worn with care.

Tanzanite’s principal, and only official source, is from a five-mile square hilltop in the Merelani Hills, in northern Tanzania. Although Tanzanite was only officially recognized in 1967, it became so well known that in 2002, by decree of the American Gem Trade Association (AGTA), it became one of the birthstones for the month of December alongside zircon and turquoise