For years the gem-mining took place on the small valley floor. Rubies
and other gems were recovered from the rich alluvium, using open-pit and loo-dwin
mining methods. In 2002 the valley floor area was mined out.
Gem mining continued at the nearby primary ruby deposit and at the numerous loos (twisted holes) and letkya (cavity filled deposit) using gwè-dwin
gem mining methods.
(mostly colorless, yellowish, purplish), spinels
(red, purple and other colors), diopside
and some quartz
are recovered. Generally most of these gems are of good quality and weigh under 5 carats; larger gems are rarely found.
Ref: Ted Themelis (2008) Gems and Mines of Mogok, p. 236