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DiamondAlluvial Diamond Mining
Mining Alluvial
The majority of the diamond deposits first discovered were alluvial -- concentrations in streambed or riverbed sand and gravel. They are still actively exploited in many ways, from the most primitive to the highly complicated. The goal is quite simple: to find a location where moving water has deposited diamonds in the bottom of a channel, possibly in a pocket or cleft. Because rivers meander and drainage can change, fossilizing a once active river, the search for alluvial diamonds requires some physical knowledge and a lot of luck. The procedure involves removing the overlying barren ground, digging up the bearing ground, extracting the diamonds, and, nowadays, restoring the landscape when finished.
In the most basic, person operations, such as in Sierra Leone or Angola, the technology involves shovel and pan, with some hand sloshing to gravitate diamond to the bottom of the pan; the eye is the ultimate sorting device. Mom-and-pop operations in South Africa involve a small claim and used a limited technology -- shovels, buckets, jury-rigged cranes powered by small vehicles, and the like -- to load a small washing pan. The focus is then sieved into several size ranges, and each fraction is dumped onto a picking table, where someone checks by eye for diamonds. Last processing includes concentrate sieving, a picking table, and usually a grease table. Of course, no crushing is required, as nature has previously released the diamonds from the pipe rock.