Is a green variety of Grossular, a Calcium Aluminum Silicate with formula Ca3Al2(SiO4)3.
Hardness is 7-7.5
Tsavorite is found generally at Tsavo National Park in Kenia, but recently other deposit have been discovered such as in the Lindi region in south Tanzania,were this stone comes from.
The color is due to traces of Vanadium and Chromium and as far as I know no enhancements has been performed up to now. Large stones achieve a very high prices in the market. This gem here is eye clean.