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.Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. Our results have significant conservation implications and emphasize the need for additional research.This article needs additional citations for verification. However, burial by dredge tailings resulted in the death of a substantial percentage of mussels of each species and no mussels were able to excavate from experimental dredge tailings. All exposed mussels survived the 6-week experiment. No obvious physical damage to mussels was observed due to entrainment by the suction dredge and entrainment had no effect on the survival of mussels. The secondary experimental treatments were exposure and burial. The primary experimental treatments were entrainment by a suction dredge versus non-entrainment. We quantified the effects of being entrained, exposed, and/or buried by suction dredge placer mining on the short-term survival of western ridged mussels ( Gonidea angulata, Lea) and western pearlshell mussels ( Margaritifera falcata, Gould) in the Similkameen River, Washington. Suction dredge placer mining is an increasingly frequent activity that may affect the survival of mussels, however, the effect of suction dredge mining on freshwater mussels has received little attention.
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