Open end pillaring - A method of mining pillars in which no stump is left; the pockets driven are open on the gob side and the roof is supported by timber. | |
Ore - a mineral aggregate of sufficient value which can be mined at a profit. | |
Orebody - the part of a vein that carries ore | |
Outcrop Rock that appears at or near the surface. | |
Overburden Layers of soil and rock covering bedrock. Overburden is removed prior to surface mining and replaced after the coal is taken from the seam. | |
Overcast (undercast) - Enclosed airway which permits one air current to pass over (under) another without interruption. | |
Oxidation - combination with oxygen |
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