Even though every rough diamond is unique, buying and selling them depends upon assigning value to agreed standards of size, shape, colour and clarity. The DTC combines these factors into 12,000 different, identifiable categories of diamonds.

Deciding how to classify any given diamond is a task that requires skill and experience. It is at the heart of what we do.

Sorting diamonds

Diamond sorting is carried out in four sorting offices:

• DTC (scheduled to relocate from London to Botswana in 2013)
• DTC Botswana in Gaborone
• DTC South Africa in Kimberley
• Namibia DTC in Windhoek

Each of these offices has its own, dedicated training academy to prepare diamond sorters to an expert level that is respected throughout the industry.

Much of the sorting operation is still carried out by experts using traditional loupes. However, in recent years, our use of proprietary advanced technology to accurately and rapidly sort larger volumes of smaller stones has given us and our producing partners competitive advantage. Technology research at our R&D facility in Maidenhead, UK emphasises simplified processes and improved value-added assortments.

Buying diamonds

We receive diamonds from our mines in South Africa and Canada and purchase diamonds from our joint venture producer partners in Botswana and Namibia. The process of agreeing value is carefully considered:

• In the interest of fairness, separate diamond sorting experts represent both DTC and the government diamond valuers (GDVs) of our joint venture partners
• Sorters classify the diamonds by comparison with master reference samples. Any disagreements are settled by reference to these samples
• Each diamond category corresponds to a price in the DTC’s proprietary price book. Once categorisation is agreed, the purchase can proceed on an agreed price

Aggregating diamonds

As a last stage, before offering diamonds to our clients, known as Sightholders, diamonds of the same category, regardless of origin, are blended. This improves the consistency of diamonds in a given category that are supplied to the Sightholders.