Exploration & Mining
 
The process that led to a natural diamond being set in an item of jewellery began as far back as 3.3 billion years ago, more than 400 kilometres more below the earth’s surface. There, under extremely high temperatures and pressures, carbon atoms were crystallised into diamonds.
 
The diamond crystals then were carried to the surface of the earth though volcanic activity, within pipes of magma known as kimberlite or lamproite. Some remained covered by earth in the remains of extinct volcanoes. Others were carried far away from their source rock by water, until they came to lay in river beds or sandy coastal areas. To diamond prospectors, diamond-rich kimberlite or lamproite mines are known as primary source mines. River bed or coastal areas yield secondary source or alluvial deposits.
 
The task of locating a diamond deposit and then mining it it is not simple. In order to extract a single carat, or 0.2 grams of diamond, an average of 250 tons of earth need to be moved.
 
The mining of primary sources occurs through open-cast mining or by digging underground mine shafts. In both cases, volcanic ore is obtained by smashing, blasting or digging, and it is then brought by truck or conveyor belt to a processing plant. There it is crushed and washed into a concentrated diamond-bearing residue. The rough diamonds are then extracted from the ore.
 
Alluvial diamond mining involves retrieving the stones from their coastal or river bed sources. Diamond crystals that were deposited in rivers are harvested, after washing with water shoveled, pumped up or dredged gravel. Riverbed mining is often done on an informal and smaller scale. Also known as artisanal digging, it frequently involves the most basic of equipment, such as sieves and pans, to find diamonds. In sandy coastal areas mining generally is done through terrace cultivation, which involves both mechanised and mechanical techniques. Undersea mining entails drilling into the seabed from specially fitted ships to recover diamond-bearing gravels.
 
Historically diamonds were mined first in India and then Brazil. The first primary source mining can be traced to the discovery of diamonds at Kimberley in South Africa in 1867. The main producer countries today in volume terms are Botswana, Russia, Canada, South Africa, Angola, Namibia, the Democratic Republic of Congo, Australia and Sierra Leone.
 
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