On average, how much rock has to be extracted in order to find an ounce of gold”?
Well, average is a good question. Currently, the largest gold mining operation in Alaska is the Fort Knox Mine near Fairbanks. In 1999 the ore grade was .95 grams per ton. At 31.1 grams per troy ounce, they must process nearly 33 tons of material to produce an ounce of gold. A very rough visualization of a ton would be a cube of material about a yard on a side (a cubic yard). Fort Knox is an example of mining a low grade ore on a very large scale. Small mines must have much better ore to operate at a profit, and so will process less material to produce an ounce of gold. A small operator might be processing material where 10-20 tons would produce an ounce of gold. I have personally worked material with a suction dredge that has had about 1/4 oz. per yard. Some rare material can be measured in ounces per ton (or yard)! While high value ore is good, most large mines are based more on the total quantity of ore available than the value of the ore, as long as the ore is good enough to turn a
