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Placer mining (pronounced "plass-er") is an open-pit or open-cast form of mining by which certain valuable minerals are extracted from the earth without tunneling; large scale excavation is accomplished using water pressure ( hydraulic mining) or surface excavating equipment. The name derives from Spanish, placer, meaning "sand bank" and refers to precious metal deposits (particularly gold and gem stones) found in alluvial deposits—deposits of sand and gravel representing stream beds. The containing material is generally too loose to safely tunnel into and 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 deposit. Where there exists sufficient water resource, hydrostatic pressure is used to mine, move, and separate the precious material from the deposit.Placers certainly supplied most of the gold for a large part of the ancient world and inclusions of platinum group metals in a very large proportion of gold items indicate that the gold was still largely derived from placer or alluvial deposits, as platinum group metals are seldom, if ever, found with gold in reef or vein deposits. In the United States, placer mining was famous in the context of several gold rushes, particularly the California gold rush. It is a source to this day in MyanmarThe Union of Myanmar is a country in Southeast Asia, formerly known as Burma . The name of the country was changed in 1989, and this change of name has been officially recognized by the United Nations. Some national governments, such as the United States and Sri LankaThe Democratic Socialist Republic of Sri Lanka (known as Ceylon before 1972) is a tropical island nation off the southeast coast of the Indian subcontinent. Known in ancient times as Lanka Lankadweepa (meaning "Resplendent Land" in Sanskrit), Taprobane an for the recovery of gems, and the KlondikeThe Klondike is a region of the Yukon Territory in northwest Canada, just east of the Alaska border. It lies around the Klondike River, a small stream that enters the Yukon River from the east at Dawson. The Klondike is famed in part because of the Klondi to recover gold.
The simplest technique of placer gold mining is panning. In panning, some sediment is placed in a large metal pan, combined with a generous amount of waterDrinking water This article focuses on water as we experience it every day. The water (molecule) article describes water from a scientific and technical perspective. Water is an abundant substance on Earth. It exists in many forms, such as sea, rain, and, and agitated so that the sand flows over the side. Any gold particles contained in the sand, due to the higher densityFor other meanings of density, see density (disambiguation Density (symbol: rho Greek: rho) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The average density of an object equals its total mass div of gold, will tend to remain on the bottom of the pan after all of the sandSand is an example of a class of materials called granular matter. Sand is a naturally occurring, finely divided rock, comprising particles or granules ranging in size from 0. 063 to 2 mm. An individual particle in this range size is termed a sand grain . and mudSee also MUD (Multi-User Dungeon). A liquid or semi-liquid mixture of water and soil, or sediment, is commonly referred to as mud . Geologically speaking, mud is a mixture of water and particles of silt and clay. Ancient mud deposits harden over geologica have been removed. The same principle may be employed on a larger scale by constructing a short length of "artificial stream bed" called a sluice box, with barriers along the bottom to slow the movement of gold particles. This method better suits excavation with shovelA shovel is a tool for lifting and moving loose material such as coal, gravel, snow, dirt, or sand. It is usually a hand tool consisting of a broad blade with edges or sides that is fixed to a medium-length handle. The term "shovel" is also applied to lars or similar implements to feed sediment into the device.
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