As a general rule metals are extracted from mineral ores. In many cases these are not present as pure metal, but in the form of compounds which contain both the metal sought and a range of other chemical elements. One example is copper. Copper ore does not contain pure copper, but either a copper-sulphur-iron compound (chalcopyrite) or a copper-sulphur compound (chalcocite). The metal must first be separated from such minerals by means of multi-step metallurgic processes. In many cases these processes are so complicated that they account for up to 30 per cent of the metal price. The metal recovered is described as “refined copper”. Mineral ores, therefore, are made up of a combination of different substances and contain only a certain amount of metal. In most cases copper ores contain between 0.6 and 1 per cent of copper. Consequently one tonne of ore generates a maximum 6 to 10 kilograms of copper. In the case of platinum the yield is much lower: 1 tonne of ore usually contains between 3 and 6 grams of platinum. Nonetheless it is still worthwhile mining because the platinum price is high. In 2013 the price per gram was around 35 Euros.