The 4 C’s are part of a well-known grading system for evaluating diamonds by grading the carat weight, color, clarity and cut. RAPLAB® grades diamonds based on the 4 C’s and several additional criteria using sophisticated technology to provide you with a more detailed and informative certification.

Various ways of “treating” a diamond, such as heat, can be used to enhance the colorlessness of a diamond or intensify the color of fancy colored diamonds. The results of these treatments can produce temporary or permanent results. However, treated stones are worth far less per carat than natural stones.


High Pressure-High Temperature (HPHT) is a process that applies extreme pressure —approximately 850,000 pounds per square inch — and very high temperature — of about 1,600 degrees centigrade — to the diamond. By altering the molecular structure of natural diamonds, HPHT greatly enhances their color. Only certain types of diamonds can be affected by this treatment, which can turn a brown diamond colorless.


This is the most popular method of making synthetic diamonds. Carbon gases are broken down in a chamber and turned into solid crystals. Controlling the temperature, types of gases and amount of pressure in the process can create different types of diamonds.


Lasers are used to minimize the appearance of flaws and make them less visible. The results of laser drilling are permanent. Drilling does leave colorless cavities in the diamond.


The irradiation of diamonds can result in the production of fancy colored stones, especially blues, greens and deep yellow. Radiation may also be used to reduce the flaws on a diamond.


This process involves painting a very thin coat of a chemical substance over the entire stone, or part of it, to improve the color. Painting neutralizes the yellow in the stone and can improve the color by as much as seven grades.