Tsavorite or tsavolite is a variety of the garnet group species grossular. Trace amounts of vanadium or chromium provide the green color.<br /> <br /> Green grossular had been rare until 1967, when British gem prospector and geologist Campbell R. Bridges came across a deposit of the mineral in the mountains of north-east Tanzania.The specimens he found were of very intense color and of high transparency. The find interested the gem trade, and attempts were made to export the stones, but the Tanzanian government did not provide permits.<br /> <br /> Believing that the deposit was a part of a larger geological structure extending possibly into Kenya, Bridges began prospecting in that nation. 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 only known to mineral specialists; in that year Tiffany and Co launched a marketing campaign which brought broader recognition of the stone.