Placer mining (pronounced "plass-er") refers to the mining of alluvial deposits for minerals. Alluvium (from the Latin, alluvius, from alluere, "to wash against" is Soil or Sediments deposited by a river or other running A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific This may be done by open-pit (also called open-cast mining) or by various forms of tunneling into ancient riverbeds. Open-pit mining, also known as opencast mining and open-cut mining and strip mining, refers to a method of extracting rock or Minerals Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body Excavation may be accomplished using water pressure (hydraulic mining), surface excavating equipment or tunneling equipment. Earthworks are engineering works created through the moving of massive quantities of Soil or unformed rock. Hydraulic mining, or hydraulicking, is a form of Mining that employs Water to dislodge rock material or move sediment
The name derives from Spanish, placera, meaning "alluvial sand. " It refers to mining the precious metal deposits (particularly gold and gemstones) found in alluvial deposits—deposits of sand and gravel in modern or ancient stream beds. Precious Metal is the eighteenth episode in the of the popular American Crime drama, which is set in Las Vegas, Nevada. Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive Mineral, which &mdash when cut and polished &mdash Alluvium (from the Latin, alluvius, from alluere, "to wash against" is Soil or Sediments deposited by a river or other running A stream bed is the channel bottom of a Stream or River or creek the physical confine of the normal water flow 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.
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History
Placers supplied most of the gold for a large part of the ancient world. Hydraulic mining methods such as hushing were used widely by the Romans across their empire, but especially in the gold fields of northern Spain after its conquest by Augustus in 25 BC. Hushing is an ancient Mining method using a flood or torrent of water to reveal mineral veins Spain () or the Kingdom of Spain (Reino de España is a country located mostly in southwestern Europe on the Iberian Peninsula. Augustus ( Latin: IMPERATOR·CAESAR·DIVI·FILIVS·AVGVSTVS September 23 63 BC – August 19 AD 14) born Gaius Octavius Thurinus, was One of the largest sites was at Las Medulas, where seven 30 mile long aqueducts were used to work the alluvial gold deposits through the first century AD. Las Médulas, located near the town of Ponferrada in León province, Spain, used to be the most important Gold mine in the Roman An aqueduct is an artificial channel that is constructed to convey water from one location to another Alluvium (from the Latin, alluvius, from alluere, "to wash against" is Soil or Sediments deposited by a river or other running (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 (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Platinum group metals are seldom found with gold in hardrock reef or vein deposits. The platinum group (alternatively the platinum group metals or platinum metals) is a collective name sometimes used for six Metallic elements ) 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. 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 (1848&ndash1855 began on January 24 1848 when Gold was discovered by James Marshall at Sutter's Mill in Coloma, California The Fraser Canyon Gold Rush, (also Fraser Gold Rush) occurred in 1858 after Gold was discovered on the Thompson River in British Columbia The Klondike Gold Rush, infrequently referred to as the Yukon Gold Rush or Alaska Gold Rush, was a frenzy of Gold rush Immigration to and for Placer mining continues in many areas of the world as a source of diamonds, industrial minerals and metals, gems (in Myanmar and Sri Lanka), platinum, and of gold (in the Yukon, Alaska and British Columbia). Burma, officially the Union of Myanmar ( pjìdàunzṵ mjàmmà nàinŋàndɔ̀ is the largest country by geographical area in mainland Southeast Asia. Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka ( Sinhalese:, இலங்கை known as Ceylon before 1972 is an Island Yukon (ˈjuːkɒn is the westernmost and smallest of Canada's three territories. Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent British Columbia (ˌbrɪtɨʃ kəˈlʌmbiə ( BC) ( (la Colombie-Britannique C Remember Kids Be Kool Stay in Skool Say Nope To Dope
Methods
The simplest technique to extract gold from placer ore is panning. In panning, some mined ore is placed in a large metal or plastic 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. Water is a common Chemical substance that is essential for the survival of all known forms of Life. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different The lighter gangue 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.
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. A sluice is a water channel that is controlled at its head by a gate This method better suits excavation with shovels or similar implements to feed ore into the device. A shovel is a Tool for lifting and moving loose material such as Coal, Gravel, Snow, Soil, or Sand and is an 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.
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 conveyor.
Environmental effects
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 common 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. The remains of a Roman alluvial gold mine at Las Medulas are so spectacular as to justify the site being designated UNESCO World Heritage status. Ancient Rome was a Civilization that grew out of a small agricultural community founded on the Italian Peninsula as early as the 10th century BC Las Médulas, located near the town of Ponferrada in León province, Spain, used to be the most important Gold mine in the Roman A UNESCO World Heritage Site is a site (such as a Forest, Mountain, Lake, Desert, Monument, Building, complex The methods used by the Roman miners are fully described by Pliny the Elder in his work Naturalis Historia published in about 77 AD. Gaius or Caius Plinius Secundus, ( AD 23 – August 25, AD 79 better known as Pliny the Elder, was an ancient Author Naturalis Historia ( Latin for "Natural History" is an Encyclopedia written Circa AD 77 by Pliny the Elder. The author was a Procurator in the region and so probably witnessed large-scale hydraulic mining of the placer deposits there. He also added that the local lake Curacado had been heavily silted by the mining methods.
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. Hydraulic mining, or hydraulicking, is a form of Mining that employs Water to dislodge rock material or move sediment Most placer mines today use settling ponds, if only to ensure that they have sufficient water to run their sluicing operations. 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 Central Valley is a large flat valley that dominates the central portion of the U San Francisco Bay is a shallow productive Estuary through which water draining from approximately forty percent of California, flowing in the Sacramento 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. The United States district courts are the general Trial courts of the United States federal court system.
References
- Assembling California, by John McPhee, published 1993 by Farrar, Straus and Giroux, New Jersey
See also
Gold prospecting is the act of going equipped to find Gold in rocks or in stream beds with a view to exploiting that discovery Hydraulic mining, or hydraulicking, is a form of Mining that employs Water to dislodge rock material or move sediment In Geology, a placer deposit or placer is an accumulation of valuable minerals formed by deposition of dense mineral phases in a trap site Gold mining in Alaska, a state of the United States, has been a major industry and impetus for exploration and settlement since a few years after the United States acquired theDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic