See Also: placer mining(encyclopedia)
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placer(2)(dictionary)
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PLACER DOME INC(finance)
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queensland (medicine) and placer mining (sh)


queensland (medicine)


queensland


A state in northeastern Australia. Its capital is brisbane. Its coast was first visited by captain cook in 1770 and its first settlement (penal) was located on moreton bay in 1824. The name cooksland was first proposed but honor to queen victoria prevailed.


placer mining (sh)




Oldest method of recovering gold from alluvial deposits.

It takes advantage of gold's high density, which causes it to sink more rapidly from moving water than the lighter siliceous materials with which it is found. Panning, used by 19th-century miners, employed a pan in which a few handfuls of the gold-bearing soil or gravel and a large amount of water were placed; by swirling the pan's contents, the miner washed the siliceous material over the side, leaving the gold and heavy materials behind. Dredging is the most important placer-mining method today. Used worldwide is the bucket-ladder dredge, with its continuous chain of buckets rotating around a rigid adjustable frame called the ladder. In sluicing, a slightly sloping wooden trough called a box sluice, or a ditch cut in hard gravel or rock called a ground sluice, is used as a channel along which gold-bearing gravel is carried by a stream of water. Riffles placed transversely along the bottom of the sluice cause the water to eddy into small basins, retarding the current so that gold may settle.