A stage in coal formation when biochemical action is exhausted
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Tag: <span>A</span>
A primitive milling process whereby ore is placed in a round, rock lined pit and milled by a series of blocks or crushers, suspended by beams radiating from the centre of the pit
The grinding of ore in a rotating cylinder using larger pieces of usually homogenous ore to grind down smaller pieces into finer grades
Sandstone with high feldspar content, usually coarse-grained and pink to red
A substance containing gold
A monatomic, inert, colourless gas. Symbol, Ar. Used in light bulbs and fluorescent tubes
A simple rotary, gear-driven drilling device
A type of rock deriving from clay or silt, also lacking the cleavage distinctive of slate