Monday, April 13, 2009

How Is Gold Mined?

The definition of gold mining is the removal of gold from the Earth, done through various techniques. There are three main types of gold extraction: placer mining/sediment mining, hard rock mining, and byproduct gold mining.

Placer mining/sediment mining is the extraction of gold from the ground with little or no excavation. Most other metals are not mined using placer mining techniques, but since gold is so valuable even in small quantities, placer mining has been used to obtain it, particularly during the California gold rush. It is still used to a limited extent today.

How is gold mined? One way is through gold panning.The main technique of placer mining is gold panning. A pan is filled with sand and pebbles that may include small pieces of gold. You add some water to the pan and shake it, and since gold is a very dense mineral it quickly settles at the bottom of the pan. This is done at placer deposits, stream beds where gold settles. Gold panning might have been viable for the independent miner during the gold rush, but is not viable for large gold deposits unless done in a place where labor costs are extremely low.

An aid to gold panning is the use of a metal detector, which the miner can use to locate gold below the surface.

Another placer mining technique is sluicing. A sluice box is a box placed in the water stream that collects gold particles as water washes through it.Gold prospecting with a sluice box

Hard rock gold mining in a pit.The next major type of gold mining is hard rock mining. This is what we most typically think of as "mining", with pits or tunnels dug into the earth to extract gold ore from the hard rock. The largest amount of new gold supplies come from hard rock mining.

Then there is byproduct gold mining. This means that the main metal being mined is not gold, but that some gold is extracted along with the main metal. For example, copper mining often results in the extraction of some gold. (It should be noted that silver is largely a byproduct of copper mining as well).

Once the miners have extracted the gold ore, how do they extract the gold from the ore? The most common method is gold cyanidation. The gold-bearing ore is finely ground, and then sodium cyanide solution is added to it. The gold and cyanide form a solution that can be separated from the rock. Then zinc is added to that extracted solution, which separates the gold from the cyanide. The zinc is then removed from the gold using sulfuric acid, leaving a gold sludge that is then ready to be smelted and refined.

That's quite a long process just to obtain gold. It is precisely because of gold's undying prestige and status as true money and preserver of wealth that we go to such lengths to obtain the precious yellow metal.

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