Tsavorite

Tsavorite is the gemological trade name for the vanadian grossular garnet discovered by the Scottish geologist C. Bridges in north-eastern Tanzania in 1967 about 10–15 km east of Komolo village, today the Lemshuku mining area. The green color of grossular is due to the substitution of aluminum by vanadium (and some chromium) in the octahedral site following the formula Ca3(Al, V, Cr)2(SiO4)3, indicating that tsavorite is a solid solution between dominant grossular and minor goldmanite. It is hosted exclusively in the metasedimentary formations from the Neoproterozoic Metamorphic Mozambique Belt. The deposits are mined in Kenya, Tanzania (Lemshuku - Merelani Hills and Ruangwa - Lindi Region), Madagascar, and other occurrences are located in Pakistan and East Antarctica. They are located within metasomatized graphitic rocks such as graphitic gneiss and calc-silicates, intercalated with meta-evaporites. Tsavorite is found as primary deposits either in nodules (type I) or in quartz vein (type II), and in places (Type III).

Tsavorite color can rival that of Emerald and unlike Emerald, it often exhibits far fewer inclusions and on occasion can be flawless. It is much rarer on earth than Emerald. 

Source:

https://www.sciencedirect.com/science/article/abs/pii/S0169136813000280#:~:text=Tsavorite%20is%20the%20gemmological%20trade,et%20al.%2C%202010b). 

https://www.minerals.net/gemstone/tsavorite_gemstone.aspx