Diamonds are the most valuable gemstones in the world. Their quality is determined by the so-called 4 Cs: cut, color, carat and clarity. Although most people are probably familiar with the word carat, the other C:s affect a diamond's value just as much (or even more) than its weight.
Carat refers to the weight of the diamond, and each carat measures 200 mg. A diamond that weighs more than one carat is more valuable than two less than one-carat diamonds together, so ideally you should try to get at least a one carat diamond. There is more to a diamond's value than its weight, though, and a small stone with a better cut and clarity can be more valuable than a bigger one that has been cut poorly or has many inclusions.
The cut refers to the proportions of the gemstone's facets. The cut affects how the diamond sparkles and reflects light, and a good cut gives a diamond its brilliance and its shine. A part of the cut is the diamond's shape (but the cut does not mean just the shape of the gemstone). The most popular shape continues to be the round brilliant, but there are many interesting alternatives to the traditional round cut: the marquise cut, the emerald cut (so called because it was originally developed for cutting emeralds) and the princess cut are also popular.
Diamond clarity refers to the amount of flaws in the gemstone. The highest grades are F (flawless) and IF (internally flawless). Completely flawless diamonds are rare, and they can be very expensive when they appear on the market. In the IF category the stones have some internal inclusions, but these are never visible to an untrained or naked eye.
White diamonds are the most popular, but diamonds are available in a range of colors from pure white to blue, pink, brown and yellow. The color can be just a pale shade of pink or blue, but there are also naturally colored diamonds that can have a clearly visible tint. White diamonds are graded as "D" and are the most valuable. At the bottom of the grading system are yellow or brown diamonds. Some naturally colored diamonds can also be quite expensive, especially if they are large samples and have a good clarity and a good cut.
Knowing the four C:s helps you to get the best diamonds you can afford. A reputable jeweler should be able to provide you with the diamond's certificate that includes its grading on all the C:s: cut, color, carat and clarity.
Sources: GIA (The Gemological Institute of America)