Gemos Gems, From the time it was established in 1991, Gemos Gems has purchased rough colored stones from East Africa. In the early 1990s, the company bought rough ruby and tanzanite in Nairobi. By the mid-1990s, Gemos Gems found that Arusha, Tanzania, was a better place to source tanzanite and began purchasing from dealers who bought the stones from Maasai tribesman.