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Economically Important Metal Concentrations in Earth’s Crust


Consider Canada, one of the world’s largest manufacturers. Canada has the largest mining regions in the world and has been one of the biggest suppliers for the last 150 years.
Canada earns a lot of income in Canada’s mining industry. Most of these are significant amounts of gold, iron, copper and potash, which are less important than nickel and diamond, but with less amounts. Revenues from the oil sector are higher than $ 100 billion annually.

The value of various Canadian mining sectors in 2013 [SE from data at http://www.nrcan.gc.ca/mining-materials/publications/8772]

A metal deposition is a rock mass in which one or more metals are concentrated to the point where it is economically suitable for recovery. Some background levels of important metals in average rocks are shown in the Table with typical grades required to form a suitable residue and their corresponding concentration factors. For example, when we look at the copper, we see that although the average rock is about 40 ppm (parts per million) of copper, about 10,000 ppm or 1% is required to obtain a suitable copper residue. In other words, copper ore contains 250 times as much copper as the typical rocks. The concentration factors for other elements in the list are much higher. 2,000 for gold and 10,000 for silver.

Typical background and ore levels of some important metals

MetalTypical Background LevelTypical Economic Grade*Concentration Factor
Copper40 ppm10,000 ppm (1%)250 times
Gold0.003 ppm6 ppm (0.006%)2,000 times
Lead10 ppm50,000 ppm (5%5,000 times
Molybdenum1 ppm1,000 ppm (0.1%)1,000 times
Nickel25 ppm20,000 ppm (2%)800 times
Silver0.1 ppm1,000 ppm (0.1%)10,000 times
Uranium2 ppm10,000 ppm (1%)5,000 times
Zinc50 ppm50,000 ppm (5%)1,000 times

It is clear that some very important concentrations need to occur in order to create a precious residue. This concentration may occur during the formation of the host rock or after rock formation by several different types of processes. There are a wide variety of ore forming processes and hundreds of mineral deposits

Economically Important Metal Concentrations in Earth’s Crust