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. Most diamonds come from the mining of kimberlite deposits. Another important source of gem diamonds, however, has been secondary alluvial deposits formed by the weathering of primary kimberlites and the subsequent deposition of released diamonds in rivers and beach gravels.
Rough or uncut diamonds are broadly classified either as gem diamonds or industrial quality diamonds, with gem representing by far the larger of the two markets by value. 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 DTC, 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.