| Placer Mining: Placer mining (pronounced "plass-er") is the mining of alluvial deposits for minerals. This may be done by open-pit (also called 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. 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. 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. Gold Panning Gold panning is a mostly manual technique of sorting gold. Wide, shallow pans are filled with sand and gravel that may contain gold. Water is added and the pans are shaken, sorting the gold from the gravel and other material. As gold is much denser than rock, it quickly settles to the bottom of the pan. The silt is usually removed from stream beds, often at a bend in the stream, or resting on the bedrock bed of the stream, where the weight of gold causes it to separate out of the water flow. This type of gold found in streams or dry streams are called placer deposits. Gold panning is the easiest technique for searching for gold, but is not commercially viable for extracting gold from large deposits, except where labor costs are very low and/or gold traces are very substantial. It is often marketed as a tourist attraction on former goldfields. Before production methods can be used, a new source must be identified and panning is a good way to identify placer gold deposits so that they may be evaluated for commercial viability. Sluice Box Using a sluice box to extract gold from placer deposits has been a common practice in prospecting and small-scale mining throughout history to the modern day. A sluice box is essentially a man-made channel with riffles set in the bottom. The riffles are designed to create dead zones in the current to allow gold to drop out of suspension. The box is placed in the stream to catch water-flow and gold bearing material is placed at the top of the box. The material is carried by water through the box where gold and other heavy material settles out behind the riffles. Lighter material flows out of the box as tailings. High-Banking Sometimes, gold bearing gravels are located some distance away from a water source, or the water source is not conducive to using a typical sluice box. The high banker pumps water from the water source to the worksite, so you don't have to carry buckets of gravel back to the creek. Dredging These are small machines floating on the water and are usually operated by one or two people. A suction dredge consists of a sluice box supported by pontoons, and attached to a suction hose which is controlled by the miner working beneath the water. Metal Detecting Can you really find gold with a metal detector? The answer is; YES! With a metal detector, a person may walk around area systematically scanning below the surface. If the meter gives a positive reading a quantity of gold may be present up to a meter below the surface. This technique is very easy to operate, highly mobile, and very popular among gold diggers. |
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Mining Methods
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Mining Company
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