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
Grading 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
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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