The four most popular factors used to measure diamond quality are cut, carat, colour and clarity. De Beers introduced this set of criteria to consumers in 1939 in order to provide consumers with a reference for evaluating diamonds.
Nature dictates the characteristics of color, clarity and carat, while cut is directly influenced by humans. The 4Cs provide scientific guidelines for evaluating diamond quality.
Carat- This term refers to the weight of a diamond. One carat is equal to about 200 milligrams. It is important not to confuse the weight of a diamond with its dimensions. Say you have two 1-carat diamonds that are both cut in the round shape -- one may appear to be larger than the other. Certain cuts allow you to see more surface area of the diamond than others. The bigger the number the bigger the diamond. However, as with the shape of the stone, it is advisable to know what size suits your hand. The average diamond engagement ring is between 0.5 and 1.00 Carat.
Cut- This term refers to the way in which the diamond has been, literally, cut -- its geometric proportions. When a diamond is emerald diamondcut, facets are created and the diamond's finished shape is determined. The number of facets has a direct impact on the brilliance, or "fire," of the diamond. Diamonds, as the following drawing illustrates, can be cut into many different shapes. The most popular shape is the round diamond , probably due in large part to the brilliance this shape can provide.Whatever the shape is, a well-cut diamond is better able to reflect light. A well cut diamond is the secret to a beautiful and brilliant diamond.
Colour- The word " colorless" could be substituted for the term "color." In referring to transparent diamonds, the color scale runs from D to J, beginning with Icy White -- the color, or lack thereof, of the most expensive diamonds -- and ending with a light yellow. The best color is no color. Diamonds allow light to be reflected and dispersed as a rainbow of color. This light dispersion, or color flash, has no effect on the technical grading of color. The absolute finest colorless stone carries a D rating, descending through each letter of the alphabet to Z, designating a diamond of light yellow, brown, or gray. This body color may be caused by the presence of trace elements, such as nitrogen, within the atomic framework of the carbon crystal. These trace elements are so minute that they are scientifically measured in parts per million (ppm). As the body color becomes more intense, the grade for color descends the scale. These gradations are so minute and precise that discerning a single grade (even by an expert) under less than ideal laboratory conditions is extremely difficult. When directly comparing diamonds for color, most consumers are unable to detect a difference unless they are at least two or three color grades apart.
Clarity- This term refers to the measurement of a diamond's flaws, or inclusions that are seen in the diamond. Clarity levels begin with Flawless and move down to Very Very Slight (VVS), Very Slight (VS) and Slightly Included (SI). Almost all diamonds contain very tiny inclusions. To determine a diamond's clarity, an expert views it under 10 power magnification. In addition to internal inclusions, surface irregularities are referred to as blemishes. These two categories of imperfections-inclusions (internal) and blemishes (external)-make up clarity. The fewer the imperfections, the rarer and more valuable the diamond. Many inclusions are not discernable to the naked eye and require magnification to become apparent. A laboratory-certified clarity rating of SI2 represents the point at which inclusions are technically not apparent to the average naked eye.