Diamonds are formed in the earth's mantle under tremendous heat and pressure and brought to the earth's surface by volcanic eruptions. These eruptions produce pipes of Kimberlite and Lamproite rock. Miners search these deposits and test them for the quantity and quality of rough diamonds they contain. If a pipe is proven to be commercially viable, mining can begin. "Open Pit" mining is often the most profitable approach. A large hole is cut into the earth as miners, explosives and machines dig into the pipe. The excavation of the pipe requires diggers to cut a "corkscrew" down into the rock allowing roads for trucks and safe access to the mine. Eventually as the mine becomes deeper, the "Pit", becomes too wide at the top and the cost to maintain the operation forces the miners to close the "Pit" or consider other options such as tunneling. Once the rock is removed from the pipe it is crushed and processed to yield its treasure.
Some diamonds are found in aluval deposits; these are rough diamonds that have been washed free from the rock by rivers and oceans . Miners dig into riverbeds and ocean floors both new and old and sift the dirt for diamonds.
Diamonds are found around the world. Botswana, South Africa, Namibia, Angola, Russia, Canada, Brazil and Australia are some of the larger producers. Crater of Diamonds State Park, located in Murfreesboro, Arkansas, is open to the public and has been yielding diamonds since 1906.