The priciple rock is scapolite marble.
At the foot of the Dan-dagu Hill rubies
and fewer sapphires
were recovered from the sandy byôn
, beneath the marble outcrops. Gem mining was carried out in an open-pit scheme, using mechanized pulsating jigs. Rubies, sapphires and spinels
of all grades, but small in size were recovered from the alluvium. Star rubies
and star blue sapphires
of all qualities were reportedly found.
Rubies were also recovered from the primary marble deposit. Near-colorless scapolite
crystals covered with whitish feldspar and other minerals were also found. In 2005 the mines were closed.
Ref: Ted Themelis (2008) Gems and Mines of Mogok, p. 240