How to Mine for Diamonds: What to Look for

Look for kimberlite pipes, or mineral deposits on the surface, to remove diamonds from an open-cast mine. Kimberlite is a rock matrix consisting of a variety of trace minerals. It is found as vertical structures underneath volcanoes and volcanic lakes, and can be a significant source of diamonds. Called "pipes," these geological formations are funnel-like tubes of rock from which the diamonds can be extracted. Because kimberlite pipes are likely to be found under "overburden," or structurally unstable material such as sand or gravel that is not suitable for tunneling, open-cast mining is done on the surface to over half a mile underground.

Use specialized machinery to unearth diamonds from an underground mine, which can go 3,281 feet in depth. However, with greater depth comes a reduced number of diamonds. Two different techniques may be used: block caving blasts large pieces of ore so that it caves under its own weight. Another method calls for mining in tiers, which is used by some mines in South Africa.

Mine alluvial deposits for diamonds through artisanal or industrial mining techniques. The former initiates the mining until the latter takes over. Artisanal mining may employ dredges and pumps to suck and separate diamonds from sediment and gravel. Industrial mining uses large machines such as draglines and hydraulic shovels, as well as explosives, to access the deposits. Alluvial diamond deposits are generally located within river terrace gravels that have traveled great distances from their origin, usually kimberlite deposits. Some of the largest and highest quality alluvial (called "placer") diamonds have been found along the Cuango River flood-plain on Africa's southwestern coast. Placer mining, or sand bank mining, extracts diamonds from these alluvial deposits; it may do so through water pressure or surface excavating equipment.

Make use of horizontal and vertical mining techniques to reach diamantiferous gravels in marine littoral deposits located offshore. Removing a large quantity of sand may be necessary, and digging more than 65 feet below sea level can be required to reach the deposits. Operations can be delicate and may need round the clock supervision. A vertical method of mining marine deposits uses a 22-foot drill head to cut into the sea bed and suck up the diamond-containing matter from the sea bed. Horizontal methods use remote-controlled underwater mining vehicles to "crawl" the sea floor and pump up gravel to the surface.