How Much Is Pure Gold Worth
Millesimal fineness is a system of denoting the purity of gold alloys by parts per thousand of pure metal by mass in the alloy. For example, an alloy containing 90% gold is denoted as “900″.
It is an extension of the older karat 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 by mass.
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.
Common Gold Purities In Millesimal Fineness
999.999(The purest gold ever produced. Refined by the Perth Mint in 1958)
999.99(The purest type of gold in the market)
999.9 (Four nines. Common in minted gold bars)
999 (Fineness equivalent to 24 carat, also known as three nines fine)
995 the minimum allowed in Good Delivery gold bars
990 also known as two nines fine
958.3 (equivalent to 23 carat)
916 (equivalent to 22 carat)
833 (equivalent to 20 carat)
750 (equivalent to 18 carat)
625 (equivalent to 15 carat)
585 (equivalent to 14 carat)
417 (equivalent to 10 carat)
375 (equivalent to 9 carat)
333 (equivalent to 8 carat; minimum standard for gold in Germany after 1884)
Karat purity is measured as 24 times the purity by mass:
X = 24 ( Mg / Mm )
X is the carat rating of the material,
Mg is the mass of pure gold or platinum in the material, and
Mm is the total mass of the material.
Therefore, 24-karat gold is fine (99.9% Au w/w), 18-karat gold is 75% gold, 12-karat gold is 50% gold, and so forth.
Common Gold Purities In Karats
24-karat (millesimal fineness 999 or higher)
22-karat (millesimal fineness 916)
21-karat (millesimal fineness 875)
20-karat (millesimal fineness 833)
18-karat (millesimal fineness 750)
15-karat (millesimal fineness 625)
14-karat (millesimal fineness 585)
10-karat (millesimal fineness 417)
9-karat (millesimal fineness 375)
8-karat (millesimal fineness 333)
1-karat (millesimal fineness 042)