Millesimal fineness

Millesimal fineness is a system of denoting the purity of platinum, gold and silver alloys by parts per thousand of pure metal in the alloy.

Related Topics:
Platinum - Gold - Silver - Alloy

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For example, an alloy containing 75% gold is denoted as "750".

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It is an extension of the older carat (karat in North American spelling) system of denoting the purity of gold by fractions of 24, such as "18 carat" for an alloy with 75% (18 parts per 24) pure gold.

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The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark, and the fineness may vary slightly from the traditional versions of purity. For example, a strict conversion of 14 carat gold would be "583.5", but in the millesimal system "585" is normally used.

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The most common millesimal finenesses used for precious metals are:

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