How are diamonds mined?
The mining methods are very diverse, depending on how diamonds present themselves at the earth’s surface. Mining of Kimberlite pipes involves ”open-pit” or ”underground mining”. When freed by erosion from the Kimberlite matrix, diamond crystals are carried along by rivers. Riverbeds are dug away and the river silt is sieved. This technique is called ”alluvial mining”. ”Marine mining” is the exploitation of sandy coastal strata by dredging. Finding diamonds can thus be the result of large industrial operations, but also of small-scale methods, or even manual labour. Diamonds are rare. It is usual that 250 tons of rock, sand and gravel must be processed to yield one carat of diamond. The annual world production amounts to approximately 100 million cts of which only 20% are of gem quality.