The old mining area has been known since the times of the Burmese kings. The largest mining scheme commenced operations in July 1992 and in 2000 was still open. Rubies
and fewer blue sapphires
of all qualities are found in the soft alluvium. The stones are recovered using lebin
and open-pit mining methods.
Ref: Ted Themelis (2008) Gems and Mines of Mogok, p. 220