Far from being the glittering stones found in jeweller's shops, freshly mined rough diamonds resemble nothing more than dull, opaque pieces of drift-glass such as you might find on the beach. Most rough diamonds reach the market through bodies such as DeBeers' Central Selling Organization (CSO), which holds 10 exclusive sales called "sights" each year in London. A private individual wishing to sell a small number of diamonds will not have access to these channels, however, nor is he likely to be able to close a deal over the Internet without some kind of face-to-face meeting. Instead, his best hope is to try local diamond cutters, dealers and bourses.
Acquaint yourself with all of the diamond's supporting documentation. Not all rough diamonds are of gem quality; those with too many imperfections are destined for industrial use. If you have any initial reports stating that your diamond has passed a quality inspection, with details such as its weight in carats, then you will be in a stronger bargaining position.
Search the Yellow Pages under headings such as "Diamond Cutters" or "Diamond Buyers" for dealers in your region. Look for well-established businesses, then make contact to find out if they would be interested in viewing a small number of uncut diamonds.
Take to the meeting any supporting documentation such as invoices and quality reports. A clear provenance will increase its value.
Go online and type the words "diamond bourse" into your search engine. A diamond bourse is a trading centre or market. Once you have found your nearest bourse, phone or e-mail them to ask about submitting rough diamonds for sale. Ideally, this will result in a situation where several dealers will compete for your goods.
An alternative is to take your rough diamonds to a professional cutter to be faceted and polished. A cut, certified stone will have much more appeal to jewellers, collectors and private buyers. The whole process, however, will require an investment of several hundred pounds.
To find a diamond bourse, you will probably have to travel to your nearest big city. Secure your diamonds somewhere other than your handbag or wallet before you set off, and don't inspect them in a public place where they might attract unwanted attention.