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Most diamonds come from the mining of kimberlite deposits. Diamondiferous pipes, which are ‘pipes’ of mineral-rich volcanic rock containing diamonds, are known as primary deposits. Diamondiferous pipes are the solidified cores of kimberlite or lamproite volcanoes.

Grading and sorting rough diamonds in Kimberley, South AfricaGrading and sorting rough diamonds in Kimberley, South Africa

Deposits that contain diamonds which have travelled some distance from their original source are referred to as secondary deposits. These deposits are formed when primary kimberlites become weathered and the diamonds are released and deposited into river beds and beach gravels. The diamonds that are now found in Namibia, for example, have travelled over 1,000 miles from their original source in southern Africa, transported by the Orange River.

Rough or uncut diamonds are broadly classified either as gem or industrial quality diamonds, with gem representing by far the larger of the two markets by value (over 99%).

The primary world market for gem diamonds is in retail jewellery, where aspects such as size, colour, shape and clarity have a large impact on valuation.

De Beers, through the Diamond Trading Company, and its partners in Botswana, South Africa and Namibia, supplies its clients - known as ‘Sightholders’ - with parcels of rough diamonds that are specifically aligned to their respective cutting and polishing needs.

Up to two-thirds of the world’s diamonds by value originate from southern and central Africa, while significant sources have been discovered in Russia, Australia and Canada.

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