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Headwall

A retaining wall at one or both ends of a culvert structure

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Headframe

The steel, concrete or timber frame at the top of a shaft usually rigged to support hoist cables

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Hard-rock mining

Mining solid ore by drilling, blasting, milling and eventually refinement of minerals generally not emplaced by any glacial activity or erosion

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Hangingwall

Mining solid ore by drilling, blasting, milling and eventually refinement of minerals generally not emplaced by any glacial activity or erosion

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Hand mining

Relatively small scale mining, usually performed for exploration purposes, utilizing hand tools such as picks, shovels, sluices, goldpans and not powered equipment

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Hammermill

A milling machine that utilizes a series of revolving hammers to pulverize falling rock led through a chute

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Hammer drill

A rock drill powered by compressed air with a clutch that allows it to not only spin the drill bit, but also a percussive hammering action

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Halide

A group of minerals whose chemical compound consists of a halogen with a more electropositive element or group

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Half-life

Term used to describe a radioisotopes decay to 50% of its current energy