Natural diamonds have been discovered in just 35 countries.
Australia, Botswana, Canada, Angola, Russia, and South Africa are among the countries that produce gem quality grade diamonds.
Natural diamonds can be found in two geological contexts. The majority are found in kimberlites, which are pipe-like structures formed by volcanic and tectonic action.
Alluvial deposits are the second geological source of diamonds. Diamonds weather over time out of their kimberlite host rock and are carried away by floods and rivers. Diamonds are then deposited in the stream sands as these streams slow down.
Diamond production can range from a few thousand to a few million carats each year. For example, between 1981 and 1991, the Finsch mine in South Africa produced approximately 5 million carats per year, whereas the production at the Argyle mine in Australia peaked at around 39 million carats.
Only about 30% of diamond mines are underground. Because the expense of underground mining is much higher and the volume of ore recovered is much lower, the diamond ore must be of relatively high value. South African mines can reach depths of nearly 4 kilometres.
Mine lifetimes in open pits can range from 2 to 50 years.