Wondrous and magical, the universally treasured diamond is truly one of nature’s phenomenons. It has been coveted, stolen, hidden away and proudly displayed in jewelry, on its own or in combination with colored gemstones, for centuries. The relentless pursuit of the diamond has destroyed lives, its acquisition, often by mysterious circumstances, has made people wealthy beyond their wildest dreams. Widely accepted as a symbol of love, celebrating the union of two hearts, a diamond’s true value is dependent upon three key quality factors; cut, color, clarity, and one simple unit of measurement, the carat; collectively known as the "four C’s."
Cut
Cut, also known as a diamond’s make, refers to the brilliance of a diamond and is all about facets; how many, their placement, and the shape and the angle at which they are cut. Think of a facet as a prism, capturing and reflecting light inside the diamond. Of the four C’s, cut is the only one determined by a skilled diamond cutter who realizes the rough diamond’s potential.
An expert cutter will cut and facet the diamond to produce the maximum amount of light inside the stone, that will be reflected from one facet to another, then disperse through the top of the stone. The goal is to produce a perfectly symmetrical stone, the right and left sides mirror images of the other. Not only must the cutter accomplish this task, but he or she must keep quantity in mind, yielding the most diamonds possible while creating the best-proportioned cut. It is a delicate balance and the cutter must often sacrifice more of the rough diamond to achieve perfection. When a cut is too deep, some light escapes through the opposite side of the pavilion; too shallow a cut will see the light also escaping through the pavilion.
The way a stone is cut can also affect its appearance in other ways. If the diamond has a deep cut, it actually looks smaller than another diamond of the same weight that is cut well. Similarly, a diamond that is cut too shallow (spread cut) will appear larger than another diamond of the same weight that is cut well. Both inexact cuts are undesirable.
Color
Lack of color in a diamond is a good thing. It is the absence of color that makes a diamond more precious than another; the whiter or more colorless the stone, the more rare. The exception to this rule is colored diamonds which occur in shades ranging through blues, greens, yellows, reds, pinks and browns. Such colored stones are exceptionally rare and often considered collector stones.
The reason colorless or whiter stones are the pinnacle of diamonds is that the lack of color allows the diamond to cleanly reflect and refract light. However, color is one of the most difficult factors to evaluate. Color differences are often so subtle as to be almost imperceptible to the eye, as well as the fact that everyone sees color differently. Even experts have difficulty judging diamond color and will often compare an ungraded stone with a previously graded one to properly determine its color. One of the reasons most diamonds are set in platinum or white gold is because it will have the least effect on the diamond’s color. A diamond with more body color looks best in yellow gold, the rich, golden tones serve to enhance the diamond’s coloration.
Color is graded by the Gemological Institute of America (GIA) with letters indicating color increments and shades:
D,E,F is colorless.
G,H,I,J is near colorless.
K,L,M is faint yellow.
N,O,P,Q,R is very light yellow.
S,T,U,V,W,X,Y,Z is light yellow.
Some diamonds naturally show a bluish tint when viewed in daylight or under fluorescent lighting. When placed in incandescent light and candlelight this bluish cast disappears. This is a result of the stone’s degree of fluorescence and is a characteristic of the stone that is not generally considered a positive or negative in its overall value.
Also see our article, "How to Buy a Diamond - Clarity and Carat" http://www.bellaonline.com/articles/art48175.asp
Reference: Barbara W. Smigel, PhD.,GG - Certified Gemologist http://www.bwsmigel.info
