Carat (mass) g or possibly up to 5 g less. Therefore, the metric equivalent of 1 "siliqua" was approximately 189 mg. The Greeks had a similar unit of the same value. Gold fineness in carats comes from carats and grains of gold in a solidus of coin. The conversion rates 1 solidus = 24 carats, 1 carat = 4 grains still stand. Woolhouse's "Measures, Weights and Moneys of all Nations" gives gold fineness in carats of 4 grains, and silver in pounds of 12 troy ounces of 20 pennyweight each. Carat (mass) The carat (ct) (not to be confused with the karat,
Troy weight by the international yard and pound agreement of 1959 as . Therefore, the troy ounce is , compared with the avoirdupois ounce, which is 437.5 grains or approximately 28.35 grams. The troy ounce, then, is about 10% heavier (ratio 192/175) than the avoirdupois ounce. Although troy ounces are still used to weigh gold, silver, and gemstones, troy weight is no longer used in most other applications. One troy ounce of gold is denoted with the ISO 4217 currency code XAU, while one troy ounce of silver is denoted as XAG. Troy weight probably takes its name from the French market