It is a natural large fissure situated at the bottom of the ridge, at the foot of Kolan hill. Rubies
and red spinels
are recovered from the primary rock through tunelling schemes. Rubies and fewer sapphires
are also found in numerous loos (twisted holes), mixed with detrital sand and gravel.
Ref: Ted Themelis (2008) Gems and Mines of Mogok, p. 227