Hallmark and fineness: what 585, 750 and 925 mean
Fineness is the share of precious metal in an alloy, in parts per thousand by weight. A hallmark is the set of marks stamped on a piece to state its fineness: 750 on 18K gold, 585 on 14K and 925 on sterling silver. Strictly, a hallmark is struck by an independent assay office after testing the metal; a number the maker stamps itself is a quality mark.
3D Jewelry Designer1 min read
What a hallmark shows
A UK hallmark has three compulsory marks: the sponsor's mark of whoever submitted the piece, the fineness mark and the assay office mark. A symbol for the metal and a date letter are optional.
Hallmarking is compulsory there: above a small exemption weight, a piece cannot be sold as precious metal without one. The United States has no compulsory assay. A maker may stamp a quality mark such as 14K or 925, and is legally responsible for its accuracy.
Common fineness marks
Gold fineness is the karat times 1000, divided by 24, so 18K is 750. Hallmarks use a short list of standard values, so 14K is marked 585 and 22K 916. In the UK the metal must be at least as fine as its mark. Sterling silver is 925, and the platinum alloys in the alloy density table are 950 and 900.
Fineness, price and weight
Precious metal is priced on its fine content: a gram of 18K holds 0.75 grams of gold. Given the spot price of the pure metal, the ring cost estimator scales it by the alloy's fineness, taking 14K as the arithmetic 583.
Fineness does not fix the density, or the weight: platinum 950 is 20.1 grams per cubic centimetre alloyed with cobalt and 21.5 with iridium. In the ring builder, each metal carries its own density.
Related
- Gold karat: what 10K, 14K, 18K and 24K mean
Karat measures gold purity in 24ths. The fineness of 9K to 24K gold, and how karat changes a ring's colour, weight and gold price.
- Ring Cost Calculator from Gold Weight
Estimate a ring's metal cost from its measured gram weight and your own price per gram. Free jewellery calculator.
- Jewelry alloy density table: gold, platinum, silver
Density of every common jewellery casting alloy in grams per cubic centimetre, with the supplier table each figure comes from.