Illustrated Mining Terms

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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.

[Picture - big dozer]

Overcast (undercast) - Enclosed airway which permits one air current to pass over (under) another without interruption.  
Oxidation - combination with oxygen

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