Definition of kobin

Gem mining method in Burma. Today it is seldom used.
It is a round pit, the walls of the pit were reinforced with logs positioned vertically forming solid fortified compartments. Halfway down the huge pit a shelf was constructed and a miner assigned to remove the accumulated water from the bottom of the pit.
This mining method was used only to mine gems from known alluvial deposits containing rich byôn.

Ref: Ted Themelis (2008) Gems and Mines of Mogok