giftsreqop.blogg.se - Dredging streambeds may be an effective technique for mining

Since gems and heavy metals like gold are considerably denser than sand, they tend to accumulate at the base of placer deposits.

The metal or gemstones, having been moved by stream flow from an original source such as a vein, are typically only a minuscule portion of the total deposit. Placer mining is frequently used for precious metal deposits (particularly gold) and gemstones, both of which are often found in alluvial deposits-deposits of sand and gravel in modern or ancient stream beds, or occasionally glacial deposits. This may be done by open-pit (also called open-cast mining) or by various surface excavating equipment or tunneling equipment. Placer mining ( / ˈ p l æ s ər/) is the mining of stream bed ( alluvial) deposits for minerals.

JSTOR ( September 2010) ( Learn how and when to remove this template message)ġ9th-century miner pouring water into a rocker box which, when rocked back and forth, will help separate gold dust from the alluvium.

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