You have probably already heard that the value of a diamond is determined by the 4 Cs: cut, color, clarity, and carat weight. But what does that really mean? What should you look for when choosing a diamond? How can you find one that best fits your budget?
First off, let's start by dispelling a common myth. Many assume that diamonds must be lit from the bottom, but in reality, diamonds are cut so that light enters the top of the stone and is reflected back out the top. Perhaps the most important step to maintain a sparkly diamond is to keep it clean. Dirt will change the angle of refraction, thus dulling the brilliance and sparkle of a diamond. Windex (with a soft toothbrush) is great cleaning agent for diamonds, and it won't leave a film on the stone.
Of the 4 Cs, cut is the most important factor that determines a diamond's "sparkle." If a stone is cut too shallow, light leaks out the bottom; too deep and it escapes through the side. The best cut is based on the proper proportion of diameter to depth, as well as final polish. It reflects the light that comes in from the top, hits both side facets and bounces back out the top of the stone, creating the most sparkle and brilliance.
Color is measured using GIA's (Gemological Institute of America) D to Z scale. All diamonds are graded on the absence of color, therefore diamonds with a higher grade (D) will have no hue.
Diamonds classified as D-F are considered colorless, G-J are near colorless, and K-M are faint yellow. Each grade could have a large price difference. Anything graded better than "I" is great for wearing in a ring. Also, if a yellower diamond is set in yellow gold, its yellow tint is not as obvious as one set in white metal. Do not confuse white diamonds that have a yellowish tint with true fancy yellow diamonds which can be very rich and beautiful.
Clarity is a measure of inclusions (internal flaws) or blemishes (external imperfections). The scale for grading clarity ranges from FL (flawless: no internal or external inclusions) to I (included: inclusions can be seen with the diamond face up and with no magnification). Within this scale there are many sub classifications.
If you are in search of a diamond to set in a ring, normally diamonds with the classification of SI1 or VS are great choices. SI1 is slightly included (the inclusions are easily visible under 10x magnification, but not to the unaided eye face-up). VS stones are very slightly included (the small inclusions are visible only under 10x magnification). Diamonds set in rings, particularly in prong settings, are susceptible to being chipped which can reduce the value of the stone by as much as half! That is why we would not recommend setting flawless or near flawless diamonds in rings.
If you are looking for a good quality diamond that won't break your budget, your best bet would be to choose a diamond that is an SI1 with H, I or J color. It looks practically flawless with the naked eye and it is nearly colorless.
Carat is a measure of a diamond's weight, and thus sizes can vary depending on the shape and cut of an individual stone. A round diamond cut with ideal proportions will typically correspond to the chart above. The cut of a diamond should be considered along with the carat weight. Poorly cut diamonds could have "hidden" weight in the base of the diamond, which will increase the carat weight, but as we talked about earlier in the section on cut, reduces the overall sparkle.