Nowadays traders presenting loose diamonds for sale must have the certificate - a special document reporting the diamond grades. Thus, certification is the fifth "C" in diamond grading. Such documents became widespread in the mid 1970s. In that time, the situation on the western market was degraded. People sought new options for investments, and the interest in diamonds increased. The certificates (Diamond Grading Reports) served to protect interests of consumers who were not competent to evaluate the quality of diamonds in the market. The certificates drew the attention to diamonds as an object for investments, and the certified diamond became a new financial tool. By that time, GIA and other diamond grading systems had been widely acknowledged, and any expert could read a certificate and judge about the diamond quality just from the reported grades even without seeing the diamond itself.

   The certificate (Diamond Grading Report) is a special document containing information on the diamond weight, color, clarity, shape, cut perfectness and indicating characteristic features of the diamond, which are determined by special gemological tests. The certificate warrants that a diamond is genuine and confrims its characteristics which determine the diamond price. The data presented in the certificate enable the stone identification, which provides an advantage for the owner in case of loss, theft, repairs, or refashioning of the jewelry, and make easier sale, storage, grading, insurance, and other procedures. The monetary value (price) of a diamond is not indicated in the certificate. If there is a need for determination and documentary confirmation of the diamond price, the Appraisal Report is prepared. Certificaiton is accomplished by the third side, which is independent of the seller, or buyer, manufacturer or vendor. The independence provides objectivity of certification.

   As a result of various economic processes, certification, which was previously conducted by numerous organizations, companies, and stores, is now provided by a few acknowledged laboratories. It was necessary to control the certification process in the market. To establish common regulations and methods of certification, the World Federation of Diamond Bourses (WFDB) and International Diamond Manufacturers' Association (IDMA) adopted the following decisions at the Amsterdam Congress in 1975:

• to establish common standards for all countries;
• to develop methods of universal introduction of these standards;
• to determine scientific aspect;
• to organize official associations acknowledged by worldwide professional companies for introduction of the international standards and methods.

   Every country has its own laws and trade experience; hence, there are no common rules for certification system, certification order, certificate contents, and rights and responsibilities of the organs dealing with certification. The International Standard Organization (ISO) worked out the Technical Report (ISO/TR 11211), which can evolve into the international standard with time.

   The common standards are still absent because diamond grading cannot be performed by simple measurements. Of the four "C", only weight can be measured directly. The main gauge for color and clarity is the human eye, and these measurements are subjective. The cut quality is a complex characteristics, and there is no commonly accepted cut grading system to date. In fact, the document issued as a result of the certification procedure has a status of laboratory report rather than certificate. However, gemological laboratories continue the development of the methods providing the maximum objectivity of grading. If a diamond is presented for certification repeatedly, a good laboratory must issue the second certificate which is identical to the first one.