So, you want to mine for gold, but you think all the placer gold in the streams near your house was found back in '49? Why not heap leach?
What is heap leach mining?
Heap leach mining is when you take ore, put in a big heap, and leach a chemical through it to remove a metal in the ore.
How to become a millionaire the heap leach mining way:
1) Find some ground that has gold in it. Not placer gold, which is chunks of gold "placed" by an outside agent (water, glacial movement, earthquake). You're looking for drill results that says the ground you're on top of has little particles of gold in it. Low-grade ore is heap leached, while higher grade ore is either processed in a conventional mill or a leach plant, but we're not talking about those.
2) Dig it up. The method of digging is up to you, but variants on strip mining are used as the gold is in particle form in those rocks.
3) Crush it up. In fact, it needs to get pretty fine, but not quite dust.
4) Dump it on your heap leach pad. Don't forget to spread it out well and lay the hoses for the upcoming liquid over it. Make sure your workers are wearing masks so you don't get nailed by the WCB for unsafe working conditions.
5) Dump cyanide over the rock. Actually, liquid sodium cyanide solution is applied (or dumped or drizzled or pored) over the ore. The theory is that the cyanide ions will link up with the little gold ions and run out in liquid format. Anyway, get on with your spraying.
6) Wait. This process takes time. Some people say you can get an 80-per-cent gold recovery over about a month. Then you change ore and begin again. This goes on until you're out of rock or out of money or out of patience.
7) Extract the gold using mysterious chemical processes. The liquid is sucked out of the bottom of the leach pad and the gold is chemically removed from the solution. The gold is carted off for further refining.
8) Clean up your poisonous mess. If you don't, the environmental people will come after you because, hey, cyanide. Also, the other people in the mining industry will kick your ass for making a black mark on mining.
9) Sell yer gold. You may want to sell it quick, as gold is currently worth $318.75 (U.S.) per ounce. That's really high, and you don't want to wait until gold bottoms out again.
Easy as pie!
No matter what you're thinking, it is possible for the heap leach mining to be done in an environmentally non-unfriendly way, not worse than the usual mining activity. However, the use of cyanide means that any kind of environmental spill can get very bad, very quickly. One example was the Summitville mine debacle back in the early 1990s. This is the classic example of how to screw up a heap leach mining operation. I'm not going to go into detail on Summitville right now, but at the bottom are some URLs to go see for yourself.
Isn't natural resource extraction fun?
http://www.epa.gov/region8/superfund/sites/sville.html (one of the best background sites)
http://toxics.usgs.gov/sites/summitville_mine.html
http://www.cdphe.state.co.us/hm/summitville.asp
http://www.hcn.org/servlets/hcn.Article?article_id=1131
http://www.usdoj.gov/enrd/summitville.htm