Because copper reacts readily with other substances, it can be found in a variety of ways in the Earth's crust. It is often found in deposits with other metals such as lead, zinc, gold and silver. By far the largest amounts of copper are found in the crust in bodies known as porphyry copper deposits. These deposits were once large masses of molten rock that cooled and solidified deep in the Earth's crust. As they cooled, some large crystals grew, which were then surrounded by smaller crystals — geologists call these rocks porphyries.

At first, the molten rock contained a small amount of copper. As it cooled and crystals began to form the amount of fluid became smaller. The copper remained in the fluid, becoming more and more concentrated. When the rock was almost completely solid, it contracted and cracked and the remaining copper-rich fluid was squeezed into the cracks, where it too finally solidified.
Over many millions of years the rocks covering these deposits eroded away and the deposits eventually appeared at the surface.

These deposits can contain 2 billion tonnes of rock which, when processed, gives 30 million tonnes of copper metal.

The word copper comes from the Latin word "cuprum", which means "ore of Cyprus". This is why the chemical symbol for copper is Cu. Copper is the only naturally occurring metal other than gold that has a distinctive colour. Like gold, copper is an excellent conductor of heat and electricity. It is also very malleable and ductile.

Copper is easily mixed with other metals to form alloys such as bronze and brass. Bronze is an alloy of tin and copper, and brass is an alloy of zinc and copper.

Copper is also resistant to corrosion (it does not rust very easily).