Tsavorite is synonymous with tsavolite (the name tsavorite proposed in honour of Tsavo National Park in Kenya) is the calcium-aluminium species of the Garnet group series grossular.
The green colour of tsavorite is due to trace amounts of chromium or vanadium. The range includes a spring-like light green, an intense blue-green and a deep forest green, all of which have a refreshing and invigorating effect. The gemstone is valuable on account of its great brilliance due to, like all garnets, having a particularly high refractive index.
The tsavorite is a young gemstone but with a very long geological history, in 1967, British gem prospector and geologist Dr Campbell R. Bridges discovered a deposit of green grossular in the mountains of north-east Tanzania.
The specimens were of very intense colour and high transparency. Interest was shown in the gem trade but the Tanzanian government did not provide the permits to export the stones. Believing that the deposit was part of a larger geological structure, Bridges extended into Kenya. He was successful a second time in 1971, when he found the mineral variety there, and was granted a permit to mine the deposit. Until 1974, the gemstone was known only to mineral specialists.
Dr Bridges was murdered in 2009 when a mob attacked him and his son on their property in Tsavo National Park, believed to be over a long running dispute over access and control of Bridges' gemstone mines. Apart from the source locality in Tanzania, it was also found in Madagascar, but so far no other occurrences of the gem material have been discovered. In late 2006, a 925 carat (185g) crystal was discovered. It yielded an oval mixed-cut 325 carat (65g) stone, one of the largest, if not the largest faceted tsavorite in the world.