The Four C's
Carat (Karat is the unit purity of gold)
All gemstones, including diamonds, have a weight which is expressed in carats. One gram is equal to 5 carats. One carat is divided into 100 "points" so that a diamond of 50 points is described as a half carat in size, or 0.50 carat. Size is one of the factors in determining the value of the diamond, but other factors such as cut, clarity and color will also effect the final price. Depending on how a stone was cut, it can look larger or smaller than a stone of equal weight (see cut).
Because of their unique optical properties, diamonds, more than any other gemstone, are capable of producing the maximum amount of brilliance. While minute crystals of diamond or other minerals are contained in almost all diamonds, a diamond that is virtually free of inclusions and surface markings will be judged as flawless. In these diamonds, nothing interferes with the passage of light or spoils the beauty. But these diamonds are extremely rare and will command a high price. To determine a diamond's clarity grading, it must be examined under a 10x magnification by a trained, skilled eye. Without magnification, you may never see these inclusions. However, the fewer there are, the rarer your diamond will be.
The most prized diamonds are colorless diamonds, because their beauty depends entirely upon their remarkable optical properties. In such diamonds, all the colors of the rainbow are reflected back to your eye. While the majority of gem diamonds appear to be colorless, others can contain increasing shades of yellow to brown, some of which are referred to as champagne diamonds. Other diamonds of exceptional color-blue, green, pink, and amber--are known as "Fancy Colored". The color grading scale varies from totally colorless to light color or tinted. The difference between one grade and its neighbor is very subtle. Experts never try to remember color; they use master diamonds of known color for comparison.
Many people confuse cut with the shape of a diamond. The shape you select is a matter of individual taste, and today your choice is only limited by the skill and imagination of the craftsman. It is their effort during every stage of the fashioning process that reflects the maximum amount of light back to the eye. Most round, brilliant-cut or fancy-shaped diamonds possess 58 carefully angled flat surfaces, called facets, whose placement will affect the fire, brilliance and ultimate beauty of your diamond. The cut of a diamond is in direct conjunction to the proportion of a diamond. With proper cutting (diagram1) the light passes through the top, reflects off the sides, and then travels back out through the top, giving the diamond optimum brilliance and dispersion. If the diamond is cut too shallow (diagram2), light passes through the bottom of the diamond. If the diamond is cut too deep (diagram3), light passes through the side of the diamond, in both cases inhibiting maximum brilliance and dispersion.