Mining Techniques for Diamonds in Africa
Diamonds are mined (extracted) within areas of Africa using several mining techniques. Three variables need to be considered to determine the best technique when extracting diamonds in modern mining: 1) The way the minerals were deposited in the ground; 2) the stability of the land surrounding the minefield; and 3) what kind of environmental damage may occur for each method of diamond extraction. One or more of several diamond extraction techniques may be used within a single African diamond mine or field.
Block Caving Extraction
Block Caving Extraction is an economical approach to mining diamonds. Using this technique, hard rock is blasted such that it caves in on itself, and is wholly dependent on the physics of gravity to extract diamonds from the broken sections of rock.
Open-Cast Mine
A common mining technique used in South Africa, particularly at the Kimberley mine or "Big Hole," requires a great deal of earth extraction. This is accomplished by removing subsoil from the "pipe," or the trails the diamond crystals traveled as they moved up through the Earth's crust millions of years ago. Hydraulic shovels are used on the subsoil, and hard rock is drilled and then blasted with explosives so it can be hauled away. A tier technique is used in which ever-narrowing concentric layers are dug to avoid having the mine collapse in upon itself.
Artisanal Mining
Artisanal mining employs the extraction of diamonds from riverbank terraces and stream beds. Diamonds become deposited in the sediment of a river or stream, and the sediment or gravel is dredged, or high-power pumps are used to suck up the sediment and gravel. Then, the diamonds are extracted from the collected gravel.
Underground Mining
Another technique is the underground mine. These mines can be dug to depths of more than 100 meters. Generally, diamond content decreases as the underground mine depth increases, and this method is more costly than open pit or open cast mining due to the requirement of more complex extraction machinery. Underground mining is done in tiers: It is a mixed method utilizing parts of both open cast and underground mining techniques. The Premier Mine in South Africa uses this technique.
Marine Littoral Deposit Mining
Marine littoral deposit mining is new and requires complex machinery and explosives to get beneath the top layers of the bed of the body of water and into the diamantiferous gravel beneath. Commonly, it is necessary to dig more than 20 meters below sea level before reaching the diamantiferous layers. A problem of watertight extraction success exists. This type of marine mining occurs both day and night, and is used mainly in Angola and Namibia.
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