Friday, January 13, 2012

Rock Review: Tanzanite

Today’s Rock Review focuses on the lovely and popular Tanzanite.

Geology Buzz

Tanzanite, dubbed this name because of its country of origin, Tanzania, is a blue to purple tone variation of a mineral called Zoisite. Tanzanite possesses a special trait called trichroism. This means that it can appear to be different colors depending on the angle it is cut or viewed from. It’s planes can either be sapphire blue, purple or burgundy. It’s appearance can also be altered under difference types of lighting. It will appear more blue under fluorescent light and more violet under incandescent light. How fascinating!

In its rough state, it doesn’t appear anything like it looks as a finished jewelry product. It actually is reddish brown in its raw form and requires heating between 550 and 700 degrees Celsius to bring out it’s blue and violet colors.

Fun Facts

Tanzanite is a very rare gem that comes from a single source in Tanzania at the foothills of Mt. Kilimanjaro. It is relatively new to the gemstone world, only being discovered in 1967 as an accidental find by a part time gold prospector, Manuel de Souza, who could not identify the stone. Originally he suspected it to be Olivine. The sample rocks traveled the “grapevine” until they eventually ended up with Hyman Saul, Vice President of Saks Fifth Avenue. He brought them to the Gemological Institute of America where geologist Ian Mc Cloud identified the mystery gem as a new variety of Zoisite. Its proper name is now Blue Zoisite, but most people know the gem under its marketing name, Tanzanite.

In its early days of discovery, some already blue/purple Tanzanite could be found in the earth due to volcanic activity. These days however, it’s unlikely to come across a find like this, which is why most Tanzanite must now be heat treated to reveal its stunning color.

The largest Tanzanite ever discovered weighed in at a staggering 737.81 carats! One of the most famous Tanzanites, “Queen of Kilimanjaro” , was set in a tiara along with 803 garnets and 913 diamonds. It is owned by Michael Scott, first CEO of Apple computers and is on display with the rest of his collection at the Gallery of Gold and Gems at the Royal Ontario Museum in Toronto, Ontario.

Queen of Kilimanjaro Tiara

Heate Treated and Untreated Tanzanite in a Grouping

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