NationMaster - Encyclopedia: Placer mining

Placer mining (pronounced "plass-er") refers to the mining of alluvial deposits for minerals. This may be done by open-pit or open-cast mining or by various forms of tunneling into ancient riverbeds. Excavation may be accomplished using water pressure (hydraulic mining), surface excavating equipment or tunneling equipment. Image File history File links X-60073. ... Image File history File links X-60073. ... The St. ... Map of California showing Los Angeles County. ... Minerals are natural compounds formed through geological processes. ... The El Chino mine located near Silver City, New Mexico is an open-pit copper mine Open-pit mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow. ... This article is about mineral extraction. ... In civil engineering, earthworks are engineering works created through the moving of massive quantities of soil or unformed stone. ... Hydraulic mining, or hydraulicking, is a form of mining that employs water under pressure to dislodge rock material or move sediment. ...

The name derives from Spanish, placer, meaning "sand bank" and refers to precious metal deposits (particularly gold and gemstones) found in alluvial deposits—deposits of sand and gravel in modern or ancient stream beds. The metal or gemstones, having been moved by stream flow from an original source such as a vein, is typically only a minuscule portion of the total deposit. The containing material may be too loose to safely mine by tunneling. Where water under pressure is available, water under pressure may be used to mine, move, and separate the precious material from the deposit. A gold nugget A precious metal is a rare metallic chemical element of high economic value. ... GOLD refers to one of the following: GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade). ... A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... Alluvium (from the Latin, alluvius, from alluere, to wash against) is soil or sediments deposited by a river or other running water. ... The bed of this stream is made up of rocks, some very rounded (having had a longer life in the stream) and some not. ...

Placers supplied most of the gold for a large part of the ancient world. (Inclusions of platinum-group metals in a very large proportion of gold items indicate that the gold was largely derived from placer or alluvial deposits. Platinum group metals are seldom, if ever, found with gold in reef or vein deposits - in the modern era only in the Tulameen River in British Columbia, Canada and on the Amur River in the Russian Far East.) In North America, placer mining was famous in the context of several gold rushes, particularly the California Gold Rush, the Fraser Canyon Gold Rush and the Klondike Gold Rush. It is a source to this day of gems in Myanmar and Sri Lanka, and of gold in the Yukon, Alaska and British Columbia. (From user talk:MyRedDice), Yes, all my images are in public domain. ... (From user talk:MyRedDice), Yes, all my images are in public domain. ... General Name, Symbol, Number platinum, Pt, 77 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Standard atomic weight 195. ... The platinum group or platinum metals is the collective name sometimes used for six chemical elements within the periodic table. ... Motto: Splendor Sine Occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English Government - Lieutenant-Governor Iona Campagnolo - Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament - House seats 36 - Senate seats 6 Confederation July 20, 1871 (6th province) Area Ranked 4th - Total 944,735 km... The Amur (Russian: Амур) (Simplified Chinese: 黑龙江; Traditional Chinese: 黑龍江; Hēilóng Jiāng, literally meaning Black Dragon River) (Mongolian: Хара-Мурэн, Khara-Muren or Black River) (Manchu: Sahaliyan Ula, literal meaning Black... Far Eastern Federal District (highlighted in red) Russian Far East (Russian: Ð”ÌÐ°Ð»ÑŒÐ½Ð¸Ð¹ Ð’Ð¾ÑÑ‚ÌÐ¾Ðº Ð Ð¾ÑÑÌÐ¸Ð¸; English transliteration: Dalny Vostok Rossii) is an informal term that refers to the Russian part of the Far East, i. ... World map showing North America A satellite composite image of North America. ... A California Gold Rush handbill A gold rush is a period of feverish migration of workers into the area of a dramatic discovery of commercial quantities of gold. ... The California Gold Rush (1848â€“1855) began on January 24, 1848, when gold was discovered at Sutters Mill. ... The Gold Rush of British Columbia occurred after gold was discovered in the Fraser River Valley. ... A typical gold mining operation, on Bonanza Creek. ... This article or section is in need of attention from an expert on the subject. ... Official language(s) none Capital Juneau Largest city Anchorage Area Ranked 1st - Total 663,267 sq mi (1,717,855 kmÂ²) - Width 808 miles (1,300 km) - Length 1,479 miles (2,380 km) - % water 13. ... Motto: Splendor Sine Occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English Government - Lieutenant-Governor Iona Campagnolo - Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament - House seats 36 - Senate seats 6 Confederation July 20, 1871 (6th province) Area Ranked 4th - Total 944,735 km...

The simplest technique to extract gold from placer ore is panning. In panning, some mined ore is placed in a large metal pan, combined with a generous amount of water, and agitated so that the gold particles, being of higher density than the other material, settle to the bottom of the pan. The lighter ore material such as sand, mud and gravel are then washed over the side of the pan, leaving the gold behind. Once a placer deposit is located by gold panning, the miner usually shifts to equipment that can treat volumes of sand and gravel more quickly and efficiently. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: Ï (rho) is the density of the substance, measured in kgÂ·m-3 m is the mass of the substance, measured in kg V is...

The same principle may be employed on a larger scale by constructing a short sluice box, with barriers along the bottom to trap the heavier gold particles as water washes them and the other material along the box. This method better suits excavation with shovels or similar implements to feed ore into the device. Similar in principle to a sluice is a rocker, a cradle-like piece of equipment that could be rocked like a cradle to sift sands through screens, which was introduced by Chinese miners in British Columbia and Australia, where the practice was referred to as "rocking the golden baby". . Another Chinese technique was the use of blankets to filter sand and gravels, catching fine gold in the fabric's weave, then burning the blankets to smelt the gold. Chinese were noted for the thoroughness of their placer extraction techniques, which included hand-washing of individual rocks as well as the complete displacement of streambeds and advanced flume and ditching techniques which became copied by other miners. Sluice gates near Henley, on the River Thames A small wooden sluice in Magome, Japan, used to power a waterwheel. ... Shovel with wide blade - especially appropriate for lifting snow or coal A shovel is a tool for lifting and moving loose material such as coal, gravel, snow, soil, or sand. ...

A trommel is composed of a slightly-inclined rotating metal tube (the 'scrubber section') with a screen at its discharge end. Lifter bars, sometimes in the form of bolted in angle iron, are attached to the interior of the scrubber section. The ore is fed into the elevated end of the trommel. Water (often under pressure) is provided to the scrubber and screen sections and the combination of water and mechanical action frees the valuable minerals from the ore. The mineral containing ore that passes through the screen is then further concentrated in smaller devices such as sluices and jigs. The larger pieces of ore that do not pass through the screen can be carried to a waste stack by a conveyer. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

Although not required, the used process water may be continuously recycled and the ore from which the sought after minerals has been extracted ("the tailings") can be reclaimed. While these recycling and reclamation processes are more commmon in modern placer mining operations they are still not universally done.

In earlier times the process water was not generally recycled and the spent ore was not reclaimed. Environmental activists describe the hydraulic mining form of placer mining as environmentally destructive because of the large amounts of silt that it adds to previously clear running streams. Most placer mines today use settling ponds, if only to ensure that they have sufficient water to run their sluicing operations. Image File history File linksMetadata Download high-resolution version (1280x960, 269 KB) Photographer: Nate Cull from Christchurch, New Zealand Title: Gold Pan Description: In the 1800s, the Wild West Coast of New Zealand was a gold miners boomtown. ... Image File history File linksMetadata Download high-resolution version (1280x960, 269 KB) Photographer: Nate Cull from Christchurch, New Zealand Title: Gold Pan Description: In the 1800s, the Wild West Coast of New Zealand was a gold miners boomtown. ... Hydraulic mining, or hydraulicking, is a form of mining that employs water under pressure to dislodge rock material or move sediment. ... A settling basin, settling pond or decant pond is a place where very fine particles from water are removed by means of gravity. ...

In California, from 1853 to 1884, "hydraulicking" of placers removed an enormous amount of material from the gold fields, material that was carried downstream and raised the level of the Central Valley by some seven feet in some areas and settled in a huge layer at the bottom of San Francisco Bay. The process raised an opposition calling themselves the "Anti-Debris Association". In January of 1884, a United States District Court banned the flushing of debris into streams, and the hydraulic mining mania in California's gold country came to an end. This article is about the Californian geographic feature. ... San Francisco Bay, San Pablo Bay, and the Golden Gate San Francisco Bay is a shallow, productive estuary through which water draining approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean. ... Map of the boundaries of the United States Courts of Appeals and United States District Courts The United States district courts are the general trial courts of the United States federal court system. ...

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