Cut refers to the exact dimensions of the diamond. The cut determines the amount of light the diamond reflects. Diamonds that reflect large amounts of light appear brilliant. If cut too shallow or too deep, a diamond appears lackluster. The price tag may be an indication of the cut. Small, well-cut diamonds cost more than their larger counterparts. Place several diamonds beside each other on a white background underneath the same lighting to compare the cut of the stones. Look at how much they appear to sparkle under the light. Pick up each stone individually and thoroughly examine it from different angles. It is important that the light's amount and quality are as consistent as possible for all of the diamonds you examine, as the diamond can only reflect the light that enters it. Even the untrained eye should be able to easily discern the quality of different cuts when multiple diamonds are viewed together.
Clarity refers to the absence of imperfections within the diamond. Look at the stone and closely inspect it for any blemishes, cloudiness or crystalline structures both within and on the surface of the stone. Ask if you may view the diamonds you are considering through a jeweler’s loupe. A loupe is a magnification device. Make certain that you view all of the stones through a loupe of the same magnification. View several diamonds through the loupe, so that you are able to compare and contrast their flaws and learn to detect subtle imperfections and differences within the stones. Flaws near the edge of the stone are preferred to flaws in the center.
Diamond color is judged on a scale of D to Z, with D representing a perfectly clear diamond and Z representing a yellow stone. The less yellow present in a diamond, the higher its quality. It is important to look at diamonds on a white background so that you can detect the presence of any yellowish hues. Also look for a bluish hue. This is called fluorescence and is also undesirable, though to a lesser degree. If you are comparing stones, it is important to take into consideration whether or not the diamond you are viewing is already mounted in jewelry. Mounted diamonds appear less yellow.
Carat refers to the weight of the diamond. Carat is an important consideration when purchasing a diamond, as it closely relates to the size of the stone and is an objective factor, one that can be easily compared across the board. If all the other features of a diamond are held constant, a larger carat stone is worth more. People are often willing to sacrifice stone quality for size, so there is an abundance of large-carat diamonds that have poor cut, clarity and color. This is an important consideration to make if you are tempted to purchase a large, inexpensively priced stone. Be certain to examine a diamond for other features beyond mere size if you want to purchase a quality stone.
Diamond certification is given by a laboratory that performs intricate examinations of individual stones and issues a certificate detailing the exact features of the stone. A diamond's certificate can be used as documentation of its value, and it can be used by an objective party to verify the identity of the stone. Accompanying certification from a reputable independent laboratory (such as the Gemological Institute of America, American Gem Society or European Gemological Laboratory) is highly desirable. It not only ensures the quality of the stone you are purchasing, it also provides you with a reliable means by which to identify your stone if it is ever stolen or tampered with.