Cochise College Student Papers in Geology
Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
Gold Mining
Erica Archer
Physical Geology
Spring 2006
Different Ways to Mine Gold
Gold mining consists of the techniques and processes in the removal of gold from the ground. Gold is a highly sought-after precious metal that for centuries has been used for many purposes; money, commodity, and in jewelry. This precious metal occurs as grains or nuggets in rocks and also in soil or sediments deposited by a river or other types of running water. Gold is a shiny, soft, yellow, dense, ductile and malleable metal.
gold nuggets gold bars
http://arizonagoldprospectors.com/index.html http://en.wikipedia.org/wiki/Image:Goldkey_logo_removed.jpg
If someone wants
to enter into the exciting world of GOLD MINING, the following
information and terminology is provided to give you a better knowledge—good luck
into your pursuit of gold.
Vocabulary
Adit—An
entrance to a mine, generally a horizontal tunnel.
Amalgamation—The
technique of using mercury to attract small particles of crushed gold and join
with them in an amalgam, or alloy. Gold may be recovered by distilling off the
mercury.
Arrastra—A
mill, consisting of one or more large stones dragged around on a circular bed,
used to grind one.
Chilean Mill—A
machine, somewhat like the arrastra, in which heavy stone wheels turn about a
central shaft and crush ore.
Cornish Pump—A
type of pump developed in Cornwall, England and commonly used in deep mines of
the nineteenth century to raise underground water.
Crosscut—A
horizontal tunnel driven perpendicular to the main direction of a vein.
Drift—An
underground tunnel which follows the course of a vein.
Footwall—The
wall or rock on the underside of a stope.
Gallery—A
drift which has been enlarged into an underground room by the extraction of ore.
Gangue—The
worthless rock in a vein which holds valuable metals.
Geology—The
science or study of rocks in the earth.
Hanging Wall—The
wall or rock on the upper or topside of an ore deposit.
Kibble—Iron
Cornish bucket used to hoist ore and miners to the surface.
Level—Horizontal
passageways or tunnels in the mine leading from the shafts, which are
established at regular intervals.
Lode—An
ore deposit occurring in place within definite boundaries separating it from the
adjoining rocks.
Metamorphism—A
pronounced change in the constitution of rock effected by pressure, hear, and
water that results in a more compact and more highly crystalline condition.
Mineral—A
substance which may or may not be of economic value, which occurs naturally in
the earth. It is homogenous, has certain chemical makeup and usually appears in
crystal or grain form.
Ore—A
mixture of mineral and gangue from which at least one of the minerals can be
extracted at a profit.
Pan—A
shallow metal dish used for washing earth and stones to separate the gold.
Placer—An
alluvial or glacial deposit containing particles of gold or other valuable
minerals.
Retort—A
vessel in which substances are distilled or decomposed by heat.
Rocker—A
device for washing gold-bearing earth to recover the precious metal.
Shaft—A
vertical entrance to a mine cut downward from the surface.
Square Set—A
set of timbers used for support in underground mining.
Stamp Mill—A
machine for crushing ore by the weight of constantly falling pieces of iron,
stone, or wood. The action approximates the pulverizing of material with a
mortar and pestle.
Stope—An
excavation created by the removal of ore and consequent widening of the drift.
Tailings—Finely
ground particles of ore deposited as waste after processing by a mill or
smelter.
Vein—An
opening, fissure, or crack in rock, containing mineralized material.
Waste—Rock
containing no ore but removed in the course of mining operations.
Whim—A
winding machine used for hoisting ore out of a shaft.
Windlass—A
device, smaller than a whim, used to raise ore from a shaft.
Winze—A vertical or inclined opening sunk from a point inside a mine.
Here are several techniques by which gold may be extracted from earth and rock:
Gold Panning
Before someone actually starts to process their first pan full of material, look around for the best location for panning. Select a spot where the water is a minimum of six inches deep and flowing just fast enough to keep the muddy water from impairing your vision of your pan and a place where you can sit down comfortably. Gold panning is a 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 rock and other material. The gravel is usually removed from streambeds, often at a bend in the stream, where the weight of gold causes it to settle out of the water flow.
gold pan
http://www.flickr.com/photos/natecull/2876115/
Gold prospecting
Gold prospecting is the act of going equipped to find gold in rocks or in stream beds with a view to exploiting that discovery. Back in the days of the Old West, prospectors searched for gold using a gold pan and a pick and shovel. The prospectors packed everything they needed on a burro and meandered across the countryside prospecting along every stream and dry wash they came to looking for signs of “color.” Up until the 20th century, gold prospecting was undertaken with the intent of securing an area to be worked exclusively. In the 20th and 21st centuries it is more commonly used to describe recreational gold hunting, especially in streams and usually on the basis of no given authority (although there are exceptions).
Using a vacuum to clean gold from bedrock.
Hunting for gold
deep in Alaska
http://arizonagoldprospectors.com/index.html
Hydraulic mining
Hydraulic mining
is a form of unearthing rock material or to move sediment by employing water
under pressure. This form of mining was used in regions like Nevada and
California, in 1853 to exploit gold. Hydraulicking was invented by the Romans to
find gold using high-pressure water jets from a tank that was situated above the
ground approximately 400-800 feet above. Hydraulic mining was used in areas
where large amounts of sand, loose gravel and/or soil that was poorly packed and
may have be washed away from a heavy stream. Water/fire hoses are also used to
remove entire hills of loose gravel, and then the gravel is run through a sluice
(a wooden trough with ripples). Since gold is heavier, it will not move as
easily as other physical objects in the sluice. This approach can damage the
environment, causing mud in streams below the mining site and erosion damage at
the site itself. The water that diverted to dry land also created mud that
destroyed habitats and flooded the land of farmers living downstream.
http://www.calgoldrush.com/graphics
Hard Rock Mining
Hard rock mining uses the most energy and this technique is used only where exceptional gold grades warrant the associated expense. This process does produce most of the world’s gold though. Hard rock mining is the procedure to remove rock from the ground, in which miners would tunnel and blast into rock, searching for deposits of gold. Veins of gold ore are often found several inches or feet wide in certain rock formations in a volcanic deposit and in certain bed layers in a sedimentary deposit. The minerals may be removed, collected, and treated to process the gold and other valuable metals from them.
Hard rock mining
These are just a few ways to mine for gold. Happy gold hunting!
Works Cited
http://www.calgoldrush.com/graphics/evolution.html
http://arizonagoldprospectors.com/index.html
http://www.e-goldprospecting.com/index.html
http://wells.entirety.ca/mining.htm
http://www.answers.com/topic/hydraulic-mining
Gold Prospectors. The Magazine for Gold, Gem, & Treasure Hunters. May/June 2000 Edition.
Johnson, M. Placer Gold Deposits of Arizona. Gems Guides Book Company. 1987.
