While many diamonds appear colorless, or white, they may actually have subtle yellow or brown tones that can be detected when comparing diamonds side by side. Colorless diamonds are the rarest and most valuable of all. Color variations are a result of the natural forces (i.e., temperature, pressure, trace elements) at work during the formation of diamonds within the Earth. Because subtle color variations dramatically affect the value of a diamond, a color grading scale is used to categorize the shading differences from one diamond to the next.
Diamonds are graded according to the GIA (Gemological Institute of America) color chart.
Clarity is an indication of a diamond‘s purity. Clarity is determined by a diamond‘s naturally occurring internal characteristics. These characteristics are sometimes not visible to the naked eye and they are what make each diamond unique. The characteristics, or inclusions, may look like crystals, feathers, clouds or dark spots and the quantity, size, and location of these inclusions does have an affect on a diamond‘s value. Diamonds with fewer and smaller inclusions generally are more brilliant, assuming that the color and cut are the same.
The U.S. Federal Trade Commission has established the jewelry industry‘s standards for diamond clarity based on 10-power magnification. A diamond is graded by its relative departure from "flawless"--the complete absence of inclusions under 10x magnification.
Less than 1% of all diamonds ever found have had no inclusions and can be called flawless (FL) or internally flawless (IF). VVS diamonds are also extremely rare. VS diamonds are of superior quality and are used in extremely fine jewelry. This clarity grade becomes more important as the diamond size increases. A large percentage of jewelry is made with SI quality diamonds. These diamonds are perfect for diamond studs or multi-stone diamond earrings, rings and bracelets or as accents in gemstone rings. I quality diamonds are acceptable as well for diamond jewelry or as accents but the sparkle is reduced by the number and location of inclusions.
Diamonds are measured in terms of weight, not size. The heavier the diamond, the greater the carat weight. Two diamonds of equal weight can have very different values, because the quality is still determined by the color, clarity and cut. As diamonds increase in size, their cost tends to increase exponentially rather than arithmetically. Thus, a one-carat diamond can cost significantly more than a one-half carat diamond of equal quality. The weight of a diamond less than one carat in size may also be described in terms of "points". There are 100 "points" in 1 carat.
Diamonds mined from the earth look like tumbled gems or beach glass. To turn the diamond into a beautiful gem, the diamond is cut with precise facets, or tiny polished faces. There are 58 total facets on the round brilliant diamond: 33 facets are in the crown and table (largest facet) located above the girdle (the diamond‘s widest point), 24 facets in the pavilion and 1 facet at the bottom, or culet.
A well cut diamond will have an amazing brilliance and fire. This is caused by white light reflecting off the diamond‘s surfaces and the mirrored depths of the pavilion. The key to desirable fire and brilliance is proportion. Light striking a shallow cut diamond will fall out the other side and not reflect back to the top. Light striking a deep cut diamond will get lost in the pavilion and also be unable to reflect back to the top.