A diamond’s color grade is based on its depth of color, or how noticeable the color in the stone is. The “normal color range” is from D-Z, covering those stones that range from completely colorless to light yellow and brown. If a diamond is graded as D, E or F, it is considered “colorless’, with a D stone being the most valuable. The G, H, I and J grades are “near-colorless.” The differences between each grade are actually very slight and are only distinguishable by a certified gemologist or laboratory equipment. Typically, diamond color begins to be noticeable to the naked-eye at about an L grade. Once a diamond goes beyond the Z color range, it moves into the fancy-color range: this includes green, pink, purple, red, and blue hues, as well as the highly-saturated yellows & browns. Diamonds that are graded as “fancy” once again begin to command a higher market value.
When people talk about a diamond’s “cut,” they are usually referring to its shape. However, for grading purposes, the word “cut” means the proportions and finish of a polished diamond. The most common (and most valuable) cut style is a standard round brilliant-cut diamond. Other well-known cuts include: princess, emerald, pear, oval, marquise, radiant and trillion. When GIA defines a diamond’s cut, it assigns one of five cut grades: Excellent, Very Good, Good, Fair, or Poor. These grades are assigned based on the proportions of the diamond’s angles, the relative measurements of its facets, the stone’s polish, and the symmetry of the cut.
Clarity is a diamond’s relative possession or absence of clarity characteristics, which are classified as either inclusions or blemishes. Inclusions are held within the stone, while blemishes are on the diamond’s surface. There are five factors that determine the overall clarity grade given to a diamond: the size, number, position, nature, and relief of the stone’s clarity characteristics. A perfect stone is a “flawless” one. The rest of the scale follows: Internally Flawless (IF), Very Very Slightly Included (VVS1 & VVS2), Very Slightly Included (VS1 and VS2), Slightly Included (SI1 and SI2), and Included (I1, I2, and I3). Typically, the human eye can only see the inclusions of an Included stone without the aid of magnification. Most inclusions became part of a diamond during the long formation process, millions of years ago. These inclusions help to identify each stone from the next; think of them as your diamond’s own personal fingerprint!
The weights of diamonds and most other gems are given in metric carats. “Carat weight” refers directly to the weight of a gemstone. One metric carat equals 0.200 grams (200 milligrams or 1/5 gram). A carat is divided into 100 equal units; these units are called points. Carat is abbreviated as “ct” or “cts” if plural. For an example, when a diamond weighs just over two carats of diamonds, it may be described as having 2.05cts. When talking about the weight of all diamonds added together in a piece of jewelry, the industry refers to "total weight"; total weight is abbreviated as "cttw." If all other factors are equal, the more a stone weighs, the more rare and valuable it will be.