A retaining wall at one or both ends of a culvert structure
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Category: <span>H</span>
The steel, concrete or timber frame at the top of a shaft usually rigged to support hoist cables
Mining solid ore by drilling, blasting, milling and eventually refinement of minerals generally not emplaced by any glacial activity or erosion
Mining solid ore by drilling, blasting, milling and eventually refinement of minerals generally not emplaced by any glacial activity or erosion
Relatively small scale mining, usually performed for exploration purposes, utilizing hand tools such as picks, shovels, sluices, goldpans and not powered equipment
A milling machine that utilizes a series of revolving hammers to pulverize falling rock led through a chute
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
Rock salt, 4[NaCl]
A group of minerals whose chemical compound consists of a halogen with a more electropositive element or group
Term used to describe a radioisotopes decay to 50% of its current energy