The carat weight measures the mass of a diamond. One carat is divided into 100 parts, or points; i.e. one-hundredth of a carat.
Clarity is a measure of internal defects of a diamond called inclusions and surfacedefects called blemishes. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. Only about 20% of all diamonds mined have a clarity rating high enough for the diamond to be considered appropriate for use as a gemstone; the other 80% are relegated to industrial use. Of that top 20%, a significant portion contains one or more visible inclusions. Those that do not have a visible inclusion are known as “eye-clean” and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry.
A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality most gem-sized natural diamonds are imperfect. The color of a diamond may be affected by chemical impurities and/or structural defects. Diamonds graded D-F are considered “colorless”, G-J are considered “near-colorless”, K-M are “slightly colored”. N-Y usually appear light yellow or brown.
Diamond cutting is the art and science of creating a gem-quality diamond out of mined rough. The cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions. Often diamond cut is confused with “shape”. The quality of a diamond’s cut is widely considered the most important of the four C’s in determining the beauty of a diamond; indeed, it is commonly acknowledged that a well-cut diamond can appear to be of greater carat weight, and have clarity and color appear to be of better grade than they actually are. The skill with which a diamond is cut determines its ability to reflect and refract light.
Diamonds do not show all of their beauty as rough stones; instead, they must be cut and polished to exhibit the characteristic fire and brilliance that diamond gemstones are known for. Diamonds are cut into a variety of shapes that are generally designed to accentuate these features. Diamonds which are not cut into a round brilliant shape are known as “fancy cuts.” These cuts include such shapes as cushion, radiant, marquise, pear, heart, oval, asscher, emerald and princess cuts.