Umba sapphire is a unique type of sapphire discovered c. 1962 in the Gerevi Hills, north of the Umba River in the Umba Valley of Tanzania. Umba sapphires exhibit coloration not common to sapphires sourced from other parts of the world, and are recovered from the alluvial deposits of the Umba River (Tanzania).
As of November 2006, the Tanzanian government prohibits export of these sapphires.
References
Umba sapphire Wikipedia(Text) CC BY-SA