Tanzanite

Tanzanite is a relatively recent discovery when compared to the other major Gemstones and is the blue or purple variety of the mineral zoisite which was discovered in the Hills of Northern Tanzania in 1967, near the city of Arusha.

Tanzanites color can appear alternately sapphire blue, violet, and burgundy depending on Crystal orientation but in it's rough state is usually a reddish brown color. It requires artificial heat treatment to 600 °C in a gemological oven to bring out the blue violet of the stone.

Because all Tanzanite is heat treated, it does not affect it's value as is the case with most other precious gemstones.

As yet, there is no laid down standard for the grading of Tanzanite for the purpose of value although a color grading is being tested, and like Emeralds, they are graded for clarity using the visual test which is that if no imperfections are visible to the naked eye, then the stone is considered flawless. Of course, size or carats is the biggest factor when assessing value.

One of the most famous large Tanzanites (242 carats) is the "Queen of Kilimanjaro". It is set in a tiara and because Tanzanite is relatively soft, it is not usually set in necklaces and earrings, so the tiara is truly a rarity. The tiara is currently on display in the Gallery of Gold and Gems at the Royal Ontario Museum in Toronto, Ontario, Canada. The exhibition is from the private collection of Michael Scott, the first CEO of Apple Computers.