GEM CUTS

SIZE AND WEIGHT

Weight is the basic measurement used to determine the size o1 gems, and the basic weight used is the carat (ct.). The origin of the word is intriguing (see Chapter 1). Briefly, it may come from either the Arabic word for carob, qirat, a tree whose pods or seeds were used as a weight by ancient lapidaries in the bazaars, or from a Greek word, keration, which is related to qirat. Thus, carat and karat are probably related. In any case, karat is used for gold and carat for gems-except in England, where both are spelled carat, with A. C..

Regardless of the origin of the word, however, the fact is this in ancient times many different kinds of seeds were used as balance{ on scales. As a result, there was no standard weight, with A.C.

being a different weight in different countries. In 1907, a standard weight was finally proposed by the International Committee On Weights and Measures. It was adopted by the United States in 190-3 and by other countries by 1930. Today, 1 carat is universally onefifth of a gram, or 200 milligrams. Since an ounce has 28.3 gram, or 200 carat is also about .007 ounce.

A carat is divided into points, with 100 points equaling 1 caratThe weight of a diamond or other gem, therefore, would be given as 2.36 points, for example, meaning that it weighs 2 carats plus 36 points.

Carats are a much more accurate measurement of gem size than any other measurement. Since gems can be cut to so many different shapes, a linear measurement could have little meaning. Although meter can be used to measure a round brilliant-cut diamond, -:,re would diameter be measured on a pear- or tear-shaped gem? meters (mm.), nevertheless, are sometimes used with both faceted and cabochon gems.