Only high-quality diamonds are suitable for use as gems. In judging the quality (and therefore the value) of a cut diamond, a buyer must take into account four criteria, known as the “four C’s”: color, clarity, carat weight, and cut. Colorless stones are extremely valuable, while yellow or brown-tinged stones are regarded as imperfect. Fancy, colored diamonds, or fancies, exhibit clear, strong colors such as blue, green, red, and orange. Fancies are quite rare and highly prized. The presence or absence of internal blemishes and flaws determines clarity. Weight reflects a diamond’s size. The unit of weight usually employed for diamonds and other gems is the metric carat, which is equal to 0.2 g (about 0.007 oz). Another unit used to express the weight of diamonds is the point, equal to 0.01 carat. A stone of 82 points would therefore weigh 0.82 carat. A 5-carat stone is worth more than five 1-carat stones that are otherwise of the same quality. The final criteria buyers use in determining the quality of a diamond is its cut. The cut is the shape and proportion of the stone, as determined during the diamond-cutting procedure.
