Copper Minerals

Copper minerals are found throughout the earth's crust. They occur in both sedimentary and igneous rocks. The outer 10 km of the crust contains 33 g of copper for every tonne of rock and in some places volcanic activity, millions of years ago, deposited molten copper in one location. It is these areas which are mined today because they contain enough copper to make mining profitable. As well as the valuable copper there is much waste rock (called gangue) which has to be removed.

Copper Ores

An ore is a rock containing enough valuable mineral to make it worth extracting. In the case of copper, it is worth extracting when there is about 2 kg of copper per 1,000 kg of ore. Copper minerals are found in over one hundred varieties although only a few have been worked for copper on a large scale (see table for most abundant copper minerals). The most abundant ores are chalcopyrite and bornite, which contain both copper and iron sulphides.  These account for about half of the worlds known ores.  Another abundant ore is cuprite (copper oxide).

Copper is an unreactive metal - it reacts only slowly with the atmosphere - so lumps of copper metal can be found buried in the ground as nuggets. This is called native copper. The largest nugget of native copper ever found came from Minnesota, USA and weighed over 400 tonnes. Native copper isn't mined as there is so little of it.