Diamond Quality Factors
Diamond is available in a range of sizes and qualities to fit every consumer’s tastes.
One of the first things most people learn about diamonds is that not all diamonds are created equal. In fact, every diamond is unique. Diamonds come in many sizes, shapes, colors, and with various internal characteristics.
All polished diamonds are valuable. That value is based on a combination of factors. Rarity is one of those factors. Diamonds with certain qualities are more rare—and more valuable—than diamonds that lack them.
Jewelry professionals use a systematic way to evaluate and discuss these factors. Otherwise, there would be no way to compare one diamond to another. And there would be no way to evaluate and discuss the qualities of an individual diamond. Diamond professionals use the grading system developed by GIA in the 1950s, which established the use of four important factors to describe and classify diamonds: Clarity, Color, Cut, and Carat Weight.
Diamonds can be fashioned into a variety of shapes and still be beautiful.
These are known as the 4Cs. When used together, they describe the quality of a finished diamond. The value of a finished diamond is based on this combination.
A diamond’s value is often affected by the rarity of one or more of the 4Cs. Colorless diamonds are scarce—most diamonds have tints of yellow or brown. So a colorless diamond rates higher on the color grading scale than a diamond that is light yellow. Value and rarity are related: In this case a colorless diamond is more rare and more valuable than one with a slight yellow color. The same relationship between rarity and value exists for clarity, cut, and carat weight.
The 4Cs describe the individual qualities of a diamond, and the value of an individual diamond is based on these qualities. The terms that people use to discuss the 4Cs have become part of an international language that jewelry professionals can use to describe and evaluate individual diamonds.
Today, the descriptions of each of the 4Cs are more precise than those applied to almost any other consumer product. And they have a long history. Three of them—color, clarity, and carat weight—were the basis for the first diamond grading system established in India over 2,000 years ago.
Subtle differences in color can dramatically affect diamond value. Two diamonds of the same clarity, weight, and cut can differ in value based on color alone. Even the slightest hint of color can make a dramatic difference in value.
This emerald cut diamond is colorless and is a D color grade. – Courtesy Lazare Kaplan Diamonds
In the normal color range, the closer a diamond gets to colorless, the higher its per-carat price. There’s an especially large leap in the price of a colorless diamond, which is extremely rare.
Diamonds come in many colors. Diamonds that range from colorless to light yellow and brown fall within the normal color range. Within that range, colorless diamonds are the most rare, so they’re the most valuable. They set the standard for grading and pricing other diamonds in the normal color range.
These diamonds—graded E, K, and Z—represent diamond colors near the top, middle, and bottom of the GIA Color Scale. – © GIA & Tino Hammid
At the GIA Laboratory, diamonds are color graded under controlled conditions by comparing them to round brilliant diamonds of known color, called masterstones.
To eliminate the guesswork from grading a diamond’s color, graders compare it to masterstones that represent known colors in the GIA D-to-Z scale. – © GIA & Tino Hammid
The GIA D-to-Z scale is the industry standard for color-grading diamonds. Each letter represents a range of color based on a diamond’s tone and saturation.
Many diamonds emit a visible light called fluorescence when they’re exposed to ultraviolet (UV) radiation. Although invisible to the human eye, UV radiation is everywhere. Sunlight contains it. Fluorescent lights emit it, too. Under the right conditions, you can see fluorescence in about 35 percent of gem diamonds.
Blue is the most common fluorescent color in gem-quality diamonds. In rare instances, fluorescence can be white, yellow, orange, or many other colors.
Strong blue fluorescence can make a light yellow diamond look closer to colorless in sunlight. Blue and yellow are color opposites and tend to cancel each other out, so blue fluorescence masks the yellow color. If the fluorescence is too strong it can make the stone look cloudy or “oily,” which can lower the value of the diamond.