A diamond certificate is the done by a third-party, not by either the diamond buyer or seller. Unfortunately, an 3rd party certification is necessary, as it would be easy for an unscrupulous jeweller to take advantage of an uninformed buyer and sell him or her a stone, which ostensibly has much better characteristics than it really does. There are a number of ways unsuspecting buyers might land a bad deal. If the diamond is not certified, there is a good chance you may be buying a stone that is one or more grades below stated values in terms of carat weight, colour, clarity, or cut. Without a certificate, issued by a reputable agency, such as GIA, IGI or HRD, a buyer relies on a jeweller’s integrity that the diamond’s 4C parameters are accurate and not overstated.