VALUATION AND PRICE
The unit of valuation by weight of gems in most countries is the carat. This term meant originally, according to some authorities, the weight of a bean of the coral tree (Erythrina), known in Africa as kuara, and used there for weighing gold-dust. Others believe the term to be derived from the Greek word Iteration, said to be the name of the fruit of a variety of acacia having seeds of remarkably uniform size. As at present employed the weight of the carat expressed in grams is about one-fifth of a gram (200 milligrams), but varies in different countries from 197 to 216 milligrams. The accepted weight in most of the large gem markets, such as Paris, London, and Berlin, varies little from 205 milligrams. This makes a carat weight a little over 3 grains troy, the exact decimal being 3.165. Hence one grain troy=0.316 carat, and one ounce troy=151.7 carats. The weight of the carat is usually given as four grains troy, but this is obviously not quite correct. The carat is subdivided into four equal parts, also known as grains, which evidently have not quite the weight of the troy grain, although the two are often confounded. The balances used for weighing gems are usually divided into sixty-fourths, and the fractional parts of a carat weight are then expressed by series of common fractions rather than by one fraction or a decimal. Thus a gem weighing 3|-35/64|- carats might have its weight expressed in this manner, 3-1/2, 1/32, 1/64. This is a record of the successive divisions of the scale met in making the weight, not reduced to a simple fraction.
The size of a stone of a given number of carats obviously varies with specific gravity of the gem; a two-carat sapphire, for instance, being a smaller stone than an emerald of the same weight. The size of diamonds of different carats weight is shown by the accompanying cuts, and they represent approximately the size of most gems of the same number of carats.
The size of a stone, besides being indicated by weight, is frequently expressed by a number. This number refers to a scale of standard sizes adopted by jewelers, which runs from 1 to 50. Thus a stone of the size of No. 12 in the scale has a weight of one-eighth of a carat, No. 24 one-half a carat, No. 38 two carats, and so on. The scale thus affords a
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