Cut is the most critical of all the variables that affect the value of a diamond. It is essential you know the quality of the cut when you are purchasing a diamond. When a diamond comes out of the ground in the very beginning, it's natural beauty is concealed. It's brilliance comes out when it is cut, which under ideal circumstances maximizes the optical properties within the diamond, particulary its ability to refract light and disperse color. Cut refers to the arrangement of a diamond's facets, not the shape of the diamond. An "Ideal Cut" diamond captures and releases the maximum play of light. To achieve this "Ideal Cut", the diamond cutter must adhere to a whole series of exacting tolerances. These tolerances may then mean that most of the diamond be cut away and not used. It has been documented that fewer than 1% of all diamonds are cut to ideal proportions. Consequently, you're likely to find truly ideal cut diamonds in only the finest stores.
Clarity is determined by the number, size, type and location of inclusions, the diamond's naturally occuring internal characteristics. The fewer and smaller the inclusions, the less they interfere with light as it passes through the diamond. Generally, the best way to see inclusions is with a binocular microscope. A 10-power maginification has been set as the standard for grading diamonds by the U.S. Federal Trade Commission. A diamond is graded by it's relative departure from "flawless"--the complete absence of inclusions under 10x magnification. A totally flawless diamond is extremely rare -- and extremely valuable. Diamonds containing many inclusions will be much lower in price. A note to keep in mind, is that a well cut diamond can minimize the appearance of inclusions. For those reasons and many more, you should consult with a gemologist that can competently evaluate both cut and clarity.
Most diamonds can appear to be white to the naked eye, but in fact they can range from colorless to yellowish, with many gradations in between. Colorless diamonds are the rarest and most valuable of all. A color grading scale is used to determine grades, due to there being many variations, this comes in very useful when used to categorize the shading differences from one diamond to the other. As the diamond increases with yellowness, it drops the value of the stone. If a diamond is well cut, brilliance and dispersion can often disguise the coloration. As you may have seen or will find out, as you shop, many jewelers lack the expertise to accurately classify a diamonds color. Many others, regardless of their expertise, may be tempted to inflate the color value in order to inflate the cost. Protect yourself by asking to see the jewelers master color-graded diamond set. As a further precaution, ask for the jewelers written assurance of the exact color grade. One of the best ways to guarantee the color of a diamond is to choose a jeweler who is competent and trustworthy. When doing this, make sure there is a title holder who has been accredited by the American Gem Society. They will be able to prove this either with a certificate or some other type of paper work stating their title. Always remember, you have to feel comfortable where you buy.
Carat Weight may be the least important of the 4 C's in determining the value of a diamond. Despite the ease of measuring weight and the relative insignificance of weight in determining the value of a diamond, there are some facts you should know and understand about the relationship between weight and price. For one thing, as diamonds increase in size, their cost tends to increase geometrically rather than arithmetically. So, a one-carat diamond can cost significantly more than one-half carat diamond of equal quality. But on the other hand, when a diamond is improperly cut, the additional weight may reduce its brilliance. For all the reasons listed, it is always advised to consult with a gemologist, to be sure you are getting what you have been told.