In the 1950’s the Gemological Institute of America® (GIA®) developed a universal grading system to objecting compare and evaluate the quality of diamonds. The grading system is called the 4Cs, which refers to the Carat, Color, Clarity, and Cut of a diamond.
Carat is the unit of weight for a diamond. Weight is typically measures to the hundred thousandth of a carat and rounded to a hundredth of a carat. Not to be confused with size, carat is evaluated by the length, width, and depth of the diamond. This means that two diamonds can have the same carat weight but have different millimeters sizes and value. It’s important to note the larger the diamond, the rarer it is. Due to this rarity, a two-carat stone will cost much more than a one-carat stone of equal quality.
The color grade of the diamond is in reference to how little color is present in the diamond. An unset diamond is given a grade, ranging from D for colorless to Z for yellow, by comparing it to stones of a known color in a controlled environment. Typically, the more “white” or colorless the diamond, the higher the grade. Even the slightest difference in grade can make a big difference in quality and price. G, H, I, and J grade diamonds are most common and provide a better value for those who are looking for near colorless diamonds.
Diamonds are formed deep within the earth and under extreme pressure and heat, which means they often include tiny imperfections called “inclusions” (internal) and “blemishes” (external). Clarity refers to the size, number, and placement of inclusions and blemishes. Diamonds with little to no imperfections receive the highest clarity grades that range from FL, for “flawless,” and I3, for “obvious inclusions.” Due to the rarity of flawless diamonds, they are the most valuable.
Cut, commonly confused with the shape of a diamond, refers to the diamond’s proportions, symmetry, and polish. Because the proportions of a diamond determine the dispersion of light that is reflected within and off the surface of the stone, the brilliance and amount of sparkle a diamond has is determined by its cut. The most perfectly proportioned diamonds have the best light reflection, whereas a shallow cut diamond lack depth and will not best reflect light.