The forty-niners with their pickaxes and burros may be long gone from the California landscape, but folks still pull gold out of the ground here in the Golden State. There’s a mining company from Vancouver, B.C. called Kore that has two potential California projects on their website. One is on the east slope of the Sierras in Long Valley, Mono County. The other is in the Sonoran desert of Imperial County, not far from the Arizona line.
A million tons of earth contains ten pounds of gold. At least, that’s roughly the frequency at which gold is distributed in the crust. It’s not uniform, of course. Gold occurs in concentrated deposits of which the famous Mother Lode is an example.
These days gold mining is done on the surface in giant pits. Much safer for the miners and much more profitable for the companies. Here’s the interesting thing: they only need one gram of gold per ton of ore to make it work.
Here’s a gram of gold, the smallest investment you can make in bullion:
A ton of ore is about 13 cubic feet or roughly 100 gallons of rock. Can you picture that? Two of those big 55-gallon oil drums. Twenty 5-gallon paint buckets. That’s how much rock you have to process in order to get the amount of gold you see in the picture.
It doesn’t seem like a lot of rock, but the Imperial project mentioned above is supposed to produce around a million troy ounces which is thirty million grams! So that’s thirty million tons of ore to process. Three thousand million gallons of rock—that’s three billion—has to be crushed and treated on-site. Mostly the stuff is piled up on top of a clay layer and some plastic and sprinkled with a cyanide solution. That reacts with the gold and the effluent is collected and the gold bits extracted via some process like carbon adsorption. Cyanide heap leaching, as the process is called, also works for silver. Copper, nickel, and uranium are also extracted using heap leaching but with sulfuric acid instead of cyanide.
They have mining trucks that can carry 200-400 tons of ore in one load. I saw haulers like that when I toured the McLaughlin Mine, the tires alone are mind-boggling. That mine, located at the intersection of Napa, Yolo, and Lake Counties produced 3.5 million troy ounces (that’s over 100 million grams) from 1985-2002. There are 38 million tons of mill tailings from that project and that does not include the overburden and material that was moved but not processed. You can’t make low-grade ores work financially unless you can deal with massive quantities of them.
Speaking of massive quantities, one of the biggest open-pit mines in the world is just outside Salt Lake City. The Rio Tinto/Kennecott Bingham Canyon Mine is two-and-a-half miles wide and half a mile deep. That is a really big hole in the ground! It has been operating for 100 years.
If you can’t grow it then you have to mine it. Californians are lucky that much of the (non-fuel) mineral wealth of their state is located in remote places like deserts and high mountains. The extraction of minerals from the earth is usually not pretty. But if we want to stay golden we have to keep digging.