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Numbers marking gold purity — 375, 585, 750, 916 — and what carats mean.
Also known as: Gold purity marks, 9ct 18ct marks, Karat
Gold purity in parts per thousand, and the carat figures they correspond to. Carat here means fineness in twenty-fourths and has nothing to do with the carat that weighs a diamond — a genuine and constant source of confusion.
Gold fineness marked in parts per thousand: 375 for 9 carat, 585 for 14 carat, 750 for 18 carat, 916 for 22 carat and 990 or 999 for near-pure gold.
Contexts: Jewellery
A carat of fineness is one twenty-fourth pure gold, so 18 carat is eighteen parts gold in twenty-four — 750 parts per thousand. Pure gold is 24 carat by definition.
Entirely unrelated to the carat that measures gemstone weight, which is a mass of 200 milligrams. The two words are homonyms with separate derivations in trade use, and confusing them is common.
A one-carat diamond and 1 carat gold have nothing in common but the spelling. American usage distinguishes them as karat and carat; British usage does not.
9 carat is legal as gold in the United Kingdom but is not recognised as gold in several other jurisdictions, where the minimum standard is higher — so a British 9 carat ring may not be saleable as gold elsewhere.
United Kingdom
A three-digit number struck inside a rectangular outline with cut corners, the shape identifying the metal as gold.
Carat marks are the gold case of the general fineness mark.