In 1931, the Gemological Institute of America established the 4 C’s grading system for diamonds. It quickly became the widely accepted measuring bar for comparing diamonds. Today, the GIA 4 C’s system is almost universally used to describe the characteristics of a diamond.
The 4 C’s Refer to the Carat, Clarity, Color, and Cut of the diamond.
The most important characteristic of a diamond to consumers is the carat weight. Apparently size does matter and consumers want it big, especially in the U.S. The carat weight is the mass of a diamond, and one carat equals 200 milligrams.
The price per carat of diamond depends on the carat weight of the diamond. The price per carat does not scale with the carat weight linearly. Since larger carat weight diamonds are rarer, the price per carat increases as the carat weight increases. There are especially high spikes in price at “milestone” weights. For example, a diamond that weights .98 carats can cost significantly less than a diamond with that is 1.02 carats with equal clarity, color, and cut. These milestone weights exist because consumers have a much greater demand for them.
The next most important characteristic of diamonds for consumers is the Clarity. The clarity measures the amount of inclusions in the diamond. Inclusions are internal flaws and defects that can be other crystals, elements, or an entirely different diamond. Inclusions also include structural deficiencies such as cracks and chips. The amount, location, visibility, size, and color of the inclusions can affect the clarity of a diamond. GIA inspects a diamond under a 10x magnification to inspect for visible defects and inclusions. As with size, the rarity of higher clarity diamond increases exponentially.
But even though consumers tend to seek diamonds based on Carat and Clarity alone, it is the Cut that helps to bring out the beauty of the diamond. Because the brilliance and shine of a diamond is based on out the light reflects inside the diamond, the cut is what largely determines the beauty of the diamond. The Cut grading refers to the proportions of angles and measurements that that determine how the like is refracted, and not the shape of the diamond. The Cut grading is based on mathematical guidelines and hard numbers unlike Clarity and Color grading, which is subjectively graded by an expert.
And finally we have the Color of the diamond. Diamonds can come in all colors of the spectrum, with some colors, like blue, increasing the value of the diamond, and other colors, like yellow, decrease the value. The grading scale for Color is alphabetical and starts from D to Z, with a D grading being a pure clear diamond. The grades D through F are diamonds that are 100% color free to the naked eye. It is widely accepted to use up to a G or H diamond when a diamond is called colorless.
These four grading scales are the most important factors in comparing a diamond. With these four pieces of information, the consumer can make a very educated estimates and comparisons when shopping for diamonds.
