How are diamonds mined? Since diamonds are so rare, it’s easy to wonder how they make it to jewelry stores. There aren’t many major diamond-producing countries in the world, but all of these countries rely on two different types of mines—open pit and alluvial.

Open Pit Diamond Mining
In an open pit mine, the magma from the center of the earth forced itself through fissures in the crust, bringing diamond crystals with it. As the magma hardened, the diamonds became embedded in the solid igneous rock. When a tube of hardened magma, called a kimberlite, is discovered with diamond crystals, mining companies conduct a series of tests and collect samples to ensure the mine will be feasible. Mining equipment is brought in to harvest the diamonds on the surface, with drilling and deeper excavation taking place over several years. The kimberlite gets exposed, broken up and hauled away to a crushing machine, which pulverizes the hard magma into smaller bits. These bits are washed, screened and further crushed. Machines that emit x-rays are used to identify diamonds from waste ore. The diamonds are extracted from the waste ore, washed and sorted for further processing.

Alluvial Mines
An alluvial mine, or placer mine, tries to access diamonds that have been broken away from their original rock beds and swept away, only to be deposited in layer after layer of sediment. This type of mining is not as organized as open pit diamond mining, in that miners attempt to sort through the sediment to find the diamonds instead of drilling into kimberlite.

Diamond Mine Locations
More than a dozen diamond-producing countries are all located in areas where geological conditions converged perfectly to form the carbon-based crystals. On the African continent, the countries of Angola, Botswana, Congo, Lesotho, Namibia, Sierra Leone, South Africa, Tanzania and Zimbabwe mostly feature open pit mines. The Venetia Diamond Mine in South Africa produces nearly half of the world’s diamonds used as gemstones. Australia’s Argyle Diamond Mine is the largest mine in the world and produces diamond commodities used for industrial purposes. Siberia, in Russia, features one of the deepest mines in the world, and India, Canada and Borneo round out the top diamond-producing countries.