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Sunset Valley
Mining Company
Mining Company
Gold Mining
Gold Mining
Gold mining consists of the processes and techniques employed in the removal of gold from the ground. There are
several techniques by which gold may be extracted from the earth.
Panning
Gold Panning is a mostly manual technique of sorting gold. Wide, shallow pans are filled with sand and gravel that may
contain gold. The pan is submerged in water and 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 panning material is usually removed from stream
beds, often at the inside turn in the stream, or resting on the bedrock bed of the stream, where the density of gold
allows it to concentrate. 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 goldfield. Before production methods can be used, a new source must be identified. Panning is a
good way to identify placer gold deposits so that they may be evaluated for commercial viability.
Metal detecting
With a metal detector, a person may walk around an area and systematically scan below the surface. The sensor can
give a positive reading for a quantity of gold to a depth of as much as a meter below the surface. As the device is easy
to operate and highly mobile, this method of prospecting is very popular among gold diggers.
Sluicing
Gold sluicing at Dilban Town, east Coat, New Zealand, 1880s 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 channel water flow. Gold-bearing
material is placed at the top of the box. The material is carried by the current through the box where gold and other
dense material settles out behind the riffles. Less dense material flows out of the box as tailings.
Larger commercial placer mining operations employ screening plants, or trammels, to remove the larger alluvial
materials, such as boulders and gravel, before concentrating the remainder in a sluice box or jig plant. These
operations typically include diesel-powered, earth-moving equipment, including excavators, bulldozers, wheel loaders
and rock trucks.
Dredging
Although this method has largely been replaced by modern methods, some dredging is done by small-scale miners
using suction dredges. These are small machines that float on the water and are usually operated by one or two people.
A suction dredge consists of a sluice box supported by pontoons, attached to a suction hose which is controlled by the
miner working beneath the water.
State dredging permits in many of the United States gold-dredging areas specify a seasonal time period and area
closures to avoid conflicts between dredgers and the spawning time of fish populations. Some states, such as Montana,
require an extensive permitting procedure, including permits from the U.S Corps of Engineers, the Montana Department
of Environmental Quality, and the local county water-quality boards.
Some large suction dredges (100 hp+ 10 inch) are used in commercial production throughout the world. Small suction
dredges are much more efficient at extracting smaller gold than the old "bucket line" was. This has improved the
chances of finding gold. Smaller dredges with 2 to 4-inch (100 mm) suction tubes are used to sample areas behind
boulders and along potential pay streaks, until "color" (gold) appears.
Other larger scale dredging operations take place on exposed river gravel bars at seasonal low water. These operations
typically use a land-based excavator to feed a gravel-screening plant and sluicebox floating in a temporary pond. The
pond is excavated in the gravel bar and filled from the natural water table. "Pay" gravel is excavated from the front face
of the pond and processed through the floating plant, with the gold trapped in the onboard sluicebox and tailings
stacked behind the plant, steadily filling in the back of the pond as the operation moves forward. This type of gold
mining is characterized by its low cost, as each rock is moved only once. It also has low environmental impact, as no
stripping of vegetation or overburden is necessary, and all process water is fully recycled. Such operations are typical
on New Zealand’s South Island and in the Klondike region of Canada.
Hard rock mining
Hard rock mining at the Associated Gold Mine, Kalgoorlie, Australia, 1951 Hard rock gold mining is done when the gold
is encased in rock, rather than found as particles in loose sediment. Hard rock mining produces most of the world's gold.
Sometimes open-pit mining is used, such as at the Ft.Knox Mine in central Alaska. Barrick Gold Corporation has one of
the largest open-pit gold mines in North America, located on its Goldstrike property in northeastern Nevada . Other gold
mines use underground mining, where the ore is extracted through tunnels or shafts. South Africa has the world's
deepest hard-rock mine, which mines gold from as deep as 3900 meters under the ground.
Byproduct gold mining
Gold is also produced by mining in which it is not the principal product. Large Copper mines, such as the Bingham
Canyon Mine in Utah , often recover considerable amounts of gold and other metals along with the copper. Some sand
and gravel pits, such as those around Denver, Colorado may recover small amounts of gold in their washing
operations. The largest-producing gold mine in the world, the Grasberg mine in Papua, Indonesia, is primarily a copper
mine.
Gold ore processing
In placer mines, the gold is recovered by gravity separation. For hardrock mining, other methods are usually used.
Cyanide process
Cyanide extraction of gold may be used in areas where fine-gold bearing rocks are found. Sodium Cyanide solution is
mixed with finely-ground rock that is proven to contain gold and/or silver, and is then separated from the ground rock as
gold cyanide and/or silver cyanide solution. Zinc is added to the solution, precipitating out residual zinc, as well as the
desirable silver and gold metals. The zinc is removed with sulfuric acid, leaving a silver and/or gold sludge that is
generally smelted into an ingot then shipped to a metals refinery for final processing into 99.9999% pure metals.
Medgold was one of the first companies to use this method.
Advancements in the 1970s have seen activated carbon used in extracting gold from the leach solution. The gold is
absorbed into the porous matrix of the carbon. Activated carbon has so much internal surface area, that fifteen grams
(half an ounce) has the equivalent surface area of the Melbourne Cricket Ground (18,100 square meters). The gold can
be removed from the carbon by using a strong solution of caustic soda and cyanide. This is known as elution. Gold is
then plated out onto steel wool through electrowinning. Gold specific resins can also be used in place of activated
carbon, or where selective separation of gold from copper or other dissolved metals is required.
The cyanide technique is very simple and straightforward to apply and a popular method for low-grade gold and silver
ore processing. Like most industrial chemical processes, there are potential environmental hazards presented with this
extraction method in addition to the high toxicity presented by the cyanide itself. This was seen in the environmental
disaster in Central-Eastern Europe in year 2000, when during the night of 30 January, a dam at a goldmine
reprocessing facility in Romania released approximately 100,000 m³ of wastewater contaminated with heavy metal
sludge and up to 120 tons of cyanide into the rivers of Tisza.
Cradle
A cradle was rocked back and forth while water was poured over it. The sand and gravel was washed through the
screen of the cradle, leaving the gold behind.
History of gold mining
Romans used hydraulic mining methods on a large scale to extract gold from extensive alluvial deposits, such as those
at Las Medulas. Mining was under the control of the state but the mines may have been leased to civilian contractors
some time later. The gold helped finance the growth of the empire, and was an important motive in the Roman invasion
of Britain by Claudius in the first century AD, although there is only one known Roman gold mine at Dolaucothi in west
Wales. Gold was a prime motivation for the campaign in Dacia when the Romans invaded Transylvania in what is now
modern Romania in the second century AD. The legions were led by the emperor Trajan, and their exploits are shown
on the grand column in City Hall. The discovery of gold in the Witwatersrand led to the Second Boer War and ultimately
the founding of South Africa.
Gold mining consists of the processes and techniques employed in the removal of gold from the ground. There are
several techniques by which gold may be extracted from the earth.
Panning
Gold Panning is a mostly manual technique of sorting gold. Wide, shallow pans are filled with sand and gravel that may
contain gold. The pan is submerged in water and 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 panning material is usually removed from stream
beds, often at the inside turn in the stream, or resting on the bedrock bed of the stream, where the density of gold
allows it to concentrate. 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 goldfield. Before production methods can be used, a new source must be identified. Panning is a
good way to identify placer gold deposits so that they may be evaluated for commercial viability.
Metal detecting
With a metal detector, a person may walk around an area and systematically scan below the surface. The sensor can
give a positive reading for a quantity of gold to a depth of as much as a meter below the surface. As the device is easy
to operate and highly mobile, this method of prospecting is very popular among gold diggers.
Sluicing
Gold sluicing at Dilban Town, east Coat, New Zealand, 1880s 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 channel water flow. Gold-bearing
material is placed at the top of the box. The material is carried by the current through the box where gold and other
dense material settles out behind the riffles. Less dense material flows out of the box as tailings.
Larger commercial placer mining operations employ screening plants, or trammels, to remove the larger alluvial
materials, such as boulders and gravel, before concentrating the remainder in a sluice box or jig plant. These
operations typically include diesel-powered, earth-moving equipment, including excavators, bulldozers, wheel loaders
and rock trucks.
Dredging
Although this method has largely been replaced by modern methods, some dredging is done by small-scale miners
using suction dredges. These are small machines that float on the water and are usually operated by one or two people.
A suction dredge consists of a sluice box supported by pontoons, attached to a suction hose which is controlled by the
miner working beneath the water.
State dredging permits in many of the United States gold-dredging areas specify a seasonal time period and area
closures to avoid conflicts between dredgers and the spawning time of fish populations. Some states, such as Montana,
require an extensive permitting procedure, including permits from the U.S Corps of Engineers, the Montana Department
of Environmental Quality, and the local county water-quality boards.
Some large suction dredges (100 hp+ 10 inch) are used in commercial production throughout the world. Small suction
dredges are much more efficient at extracting smaller gold than the old "bucket line" was. This has improved the
chances of finding gold. Smaller dredges with 2 to 4-inch (100 mm) suction tubes are used to sample areas behind
boulders and along potential pay streaks, until "color" (gold) appears.
Other larger scale dredging operations take place on exposed river gravel bars at seasonal low water. These operations
typically use a land-based excavator to feed a gravel-screening plant and sluicebox floating in a temporary pond. The
pond is excavated in the gravel bar and filled from the natural water table. "Pay" gravel is excavated from the front face
of the pond and processed through the floating plant, with the gold trapped in the onboard sluicebox and tailings
stacked behind the plant, steadily filling in the back of the pond as the operation moves forward. This type of gold
mining is characterized by its low cost, as each rock is moved only once. It also has low environmental impact, as no
stripping of vegetation or overburden is necessary, and all process water is fully recycled. Such operations are typical
on New Zealand’s South Island and in the Klondike region of Canada.
Hard rock mining
Hard rock mining at the Associated Gold Mine, Kalgoorlie, Australia, 1951 Hard rock gold mining is done when the gold
is encased in rock, rather than found as particles in loose sediment. Hard rock mining produces most of the world's gold.
Sometimes open-pit mining is used, such as at the Ft.Knox Mine in central Alaska. Barrick Gold Corporation has one of
the largest open-pit gold mines in North America, located on its Goldstrike property in northeastern Nevada . Other gold
mines use underground mining, where the ore is extracted through tunnels or shafts. South Africa has the world's
deepest hard-rock mine, which mines gold from as deep as 3900 meters under the ground.
Byproduct gold mining
Gold is also produced by mining in which it is not the principal product. Large Copper mines, such as the Bingham
Canyon Mine in Utah , often recover considerable amounts of gold and other metals along with the copper. Some sand
and gravel pits, such as those around Denver, Colorado may recover small amounts of gold in their washing
operations. The largest-producing gold mine in the world, the Grasberg mine in Papua, Indonesia, is primarily a copper
mine.
Gold ore processing
In placer mines, the gold is recovered by gravity separation. For hardrock mining, other methods are usually used.
Cyanide process
Cyanide extraction of gold may be used in areas where fine-gold bearing rocks are found. Sodium Cyanide solution is
mixed with finely-ground rock that is proven to contain gold and/or silver, and is then separated from the ground rock as
gold cyanide and/or silver cyanide solution. Zinc is added to the solution, precipitating out residual zinc, as well as the
desirable silver and gold metals. The zinc is removed with sulfuric acid, leaving a silver and/or gold sludge that is
generally smelted into an ingot then shipped to a metals refinery for final processing into 99.9999% pure metals.
Medgold was one of the first companies to use this method.
Advancements in the 1970s have seen activated carbon used in extracting gold from the leach solution. The gold is
absorbed into the porous matrix of the carbon. Activated carbon has so much internal surface area, that fifteen grams
(half an ounce) has the equivalent surface area of the Melbourne Cricket Ground (18,100 square meters). The gold can
be removed from the carbon by using a strong solution of caustic soda and cyanide. This is known as elution. Gold is
then plated out onto steel wool through electrowinning. Gold specific resins can also be used in place of activated
carbon, or where selective separation of gold from copper or other dissolved metals is required.
The cyanide technique is very simple and straightforward to apply and a popular method for low-grade gold and silver
ore processing. Like most industrial chemical processes, there are potential environmental hazards presented with this
extraction method in addition to the high toxicity presented by the cyanide itself. This was seen in the environmental
disaster in Central-Eastern Europe in year 2000, when during the night of 30 January, a dam at a goldmine
reprocessing facility in Romania released approximately 100,000 m³ of wastewater contaminated with heavy metal
sludge and up to 120 tons of cyanide into the rivers of Tisza.
Cradle
A cradle was rocked back and forth while water was poured over it. The sand and gravel was washed through the
screen of the cradle, leaving the gold behind.
History of gold mining
Romans used hydraulic mining methods on a large scale to extract gold from extensive alluvial deposits, such as those
at Las Medulas. Mining was under the control of the state but the mines may have been leased to civilian contractors
some time later. The gold helped finance the growth of the empire, and was an important motive in the Roman invasion
of Britain by Claudius in the first century AD, although there is only one known Roman gold mine at Dolaucothi in west
Wales. Gold was a prime motivation for the campaign in Dacia when the Romans invaded Transylvania in what is now
modern Romania in the second century AD. The legions were led by the emperor Trajan, and their exploits are shown
on the grand column in City Hall. The discovery of gold in the Witwatersrand led to the Second Boer War and ultimately
the founding of South Africa.
