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How is Gold Mined?
There are several different methods of mining gold.
There are four main types of gold mining: placer mining, hard rock mining, byproduct mining, and gold ore processing.
Methods of Gold Mining
Placer mining is the process of mining gold that has already been concentrated in a deposit.
Placer mining aims to separate alluvial or residual deposits into their constituent parts, just as gold ore would be processed when taken from underground deposits.
Using pans, sluice boxes, and other tools, placer miners can use simple hand tools to separate rocks and gravel in an area containing heavy concentrations of gold.
The most common form of placer mining is panning.
Panning for gold involves using a pan or trough with high sides and a bottom made of riffles.
Gravel and dirt from the river are scooped into the pan, and water is poured in.
The lighter materials (gravel, dirt) float away, while the heavier gold sinks to the bottom into the riffles. Gold pans can be bought online or at your local camping goods store if you're interested in trying out this rewarding hobby!
Another method of extracting heavy concentrations of gold uses a sluice box instead of a prospector's pan.
Sluices have been used since ancient times to extract gold from sedimentary deposits by washing away lighter materials and capturing gold in the riffles.
Although sluices are capable of removing tiny particles of gold from gravel washed downstream, they are most effective when used on sections of the river where the water is deep enough to prevent the lighter material - sand, silt, etc. - from washing away before it encounters a bend or an obstruction which slows down the current
Although operating off the same principles as panning and sluicing, gold dredging uses heavy machinery that requires more capital outlay but greater efficiency to operate.
Gold dredges consist of a suction hose that sucks up gravel and other sedimentary deposits along river beds, releasing them through sluice boxes at higher speeds than manual methods can compete with.
Gold dredges were a popular mining method during the North American gold rush of the mid-1800s, and they are still used today in California by hobbyists and commercial operations alike.
4. Rocker Box
The final way placer mining extracts gold is with a rocker box also called a cradler box or cradle for short. A rocker is less effective than either sluicing or dredging.
Still, it requires no expensive mining equipment to operate.
It can be done with relative ease on any river where heavy concentrations of alluvial deposits have accumulated over long periods.
Also known as a rocking cradle - since this is essentially a crude rocking chair you sit upon with your feet braced on either side of a rectangular box - the rocker is designed to exploit natural forces, namely gravity, and electromagnetism.
A cradler box can be loaded with gold-laden material then rocked back and forth rapidly in the water. The rapid motion causes heavier materials to tumble out of the box while lighter gravel washes away after being swept up by the current.
Hard Rock Mining
Hard rock mining is the process of extracting gold from deep within the earth.
Hard rock mining includes all types of deposits, including lode mines and placer mines.
Hard rock mining requires heavy machinery, specialized tools, power equipment, significant financing, and workers to extract gold ore safely while creating minimal environmental impact.
Hard rock miners must be prepared for difficult working conditions underground and hazardous conditions that require strict safety precautions.
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Byproduct mining is any type of deposit that contains more byproduct materials than actual gold ore.
Depending on what material it produces mostly, a deposit can belong to one of several classification groups:
diamonds are considered "industrial minerals," sapphires are considered "gemstones," and nickel, copper, zinc, and lead are classified as "base metals."
Gold Ore Processing
After gold is mined from the ground and taken to a facility, Gold Ore Processing must occur.
The first step at this facility is when the gold-containing material, known as tailings, is crushed into a fine powder. This process allows for the efficient removal of large rocks that could slow down or jam up water pumps used in processing.
Then, chemicals such as cyanide (which bonds to gold) will leech out the pure microscopic particles of gold from each other; then mercury (which also has a strong attraction to pure gold) will be added to form an alloy called amalgam.
This amalgam is then heated to vaporize off the mercury, leaving behind only pure gold.
Finally, the gold will be poured into molds, forming bricks or bars for easier transportation and storage.
Process with cyanide
After gold ore is mined from the ground and taken to a facility, Gold Ore Processing must occur. Cyanide (which bonds to gold) is added to each mixture of crushed rock and water; then mercury (which also has a strong attraction to pure gold) is added and heated.
The resulting amalgam material formed by this process will be removed and heated until the mercury vaporizes off, leaving behind only pure gold particles.
One of the most common ways people believe they can find gold is by using mercury at home or on public lands.
While some amateurs use such methods successfully, it's done far too often without checking for possible dangers - including more serious issues such as the contamination of water supplies and poisoning wild animals.
Process with mercury
The process used to extract gold with mercury is as follows:
Step 1. Crush the ore into fine dust using a hammer or pulverizer, then place it into a container and add water.
Step 2. Add mercury (also called quicksilver) and shake the container vigorously for around 15 minutes; this allows the particles of gold (which has an extremely high weight ratio) to separate from other materials in the crushed rock because gold is heavier than almost everything but mercury. Shake it until no more sediment settles at the bottom of your storage area; this will be very obvious since all settled material will have turned black from being mixed together during shaking.
Step 3. Pour off most of the water, leaving just enough so that the materials inside are damp.
Step 4. Place the container with the remaining contents onto a hot plate and begin heating it (not to exceed 350 degrees Fahrenheit). This will release toxic fumes of mercury, so make sure you do this process in a well-ventilated area or outside. Be careful also not to touch or breath in any of the evaporated mercury that comes out during this step - even though there usually isn't enough to harm you just by being around it via inhalation, touching your skin with it can give you quite heavy metal poisoning.
Step 5. Add more crushed rock material to the now-empty storage container once all visible amounts of mercury have evaporated away, then shake/mix thoroughly again for 15 minutes before allowing the debris to settle again. You may need to repeat this process multiple times (3-4 times typically works) to get all of the particles separated.