However over the last few years, the industry has experienced difficulties with the fall in global coal prices which have placed considerable financial pressure on operators.
Fodd bynnag, dros yr ychydig flynyddoedd diwethaf, mae’r diwydiant wedi gorfod dygymod ag anawsterau, gyda’r cwymp ym mhris glo ar y marchnadoedd rhyngwladol yn rhoi pwysau aruthrol ar gwmnïau.