Methods of extracting metals

Methods of extracting metals

The Earth's crust contains metals and metal compounds such as gold, iron oxide and aluminium oxide, but when found in the Earth these are often mixed with other substances. To be useful, the metals have to be extracted from whatever they are mixed with. A metal ore is a rock containing a metal, or a metal compound, in a high enough concentration to make it economic to extract the metal.

The method used to extract metals from the ore in which they are found depends on their reactivity. For example, reactive metals such as aluminium are extracted by electrolysis, while a less-reactive metal such as iron may be extracted byreduction with carbon or carbon monoxide.

Thus the method of extraction of a metal from its ore depends on the metal's position in the reactivity series:

Reactivity and extraction method

Metals - in decreasing order of reactivity	Reactivity
potassium sodium calcium magnesium aluminium	extract by electrolysis
carbon
zinc iron tin lead	extract by reaction with carbon or carbon monoxide
hydrogen
copper silver gold platinum	extracted by various chemical reactions

Note that gold, because it is so unreactive, is found as the native metal and not as a compound, so it does not need to be chemically separated. However, chemical reactions may be needed to remove other elements that might contaminate the metal.