Whether as a gift for a loved one or a personal investment, the purchase of a diamond is one seldom entered into lightly. Even when dealing with a trusted jeweller, most people would like to have some idea of what it is that separates a good quality diamond from a poor quality one. Unfortunately, for most of us, buying a diamond is not an every day occurrence, and most people have no idea how to choose a diamond when the time comes to actually buy one.

The GIA (Gemological Institute of America) has established a classification system for the rating and valuation of diamonds, complete with a handy memory aid. The classification of diamonds is done by the ‘four Cs’: Cut, Carat, Color, and Clarity.

The most critical factor in the valuation of a diamond is the cut. While the particular shape is more a matter of personal preference than anything, the quality of the cut itself is of the utmost importance. The cut must be carried out by a master diamond cutter to work with the diamond’s natural facets. A properly cut diamond should be, above all, brilliant. Each facet should be cut and polished to show off the lustre and brilliance of the diamond and allow it to reach its maximum potential.

Carat, the quality most people are familiar with, is a measure of weight, not size. However, the two should be relative, so in an authentic diamond, a particular carat weight should equal a certain size. While a large diamond is nice, a higher quality diamond should be cut in a way that complements its natural size and shape, and not merely for a larger size. While a high carat value is a desirable attribute in a diamond, it is far from the most important factor.

Diamonds range from completely colorless to vivid yellow, with most falling somewhere in between. The color of a diamond is rated on an alphabetic scale from D to Z, with D being colorless, the rarest and most expensive variety, and Z being vivid yellow.

Clarity is the final criterion for the value of a diamond, and is a reference to the size and presence of tiny defect known as inclusions, a relic of the hardening process of the diamond itself. While most diamonds do have some inclusions, and they are actually a sign of authenticity, a large or noticeable inclusion will negatively affect the refraction of the diamond. Thus, the fewer and smaller the inclusions, the rarer and more valuable the diamond.