Fineness or purity denotes the content of gold in proportion to the total weight in various gold products, such as coins, bars, and jewelry. Millesimal fineness is a system to denote the purity of pure gold by mass in the alloy. It is expressed in units of parts per 1000.
Bullion gold typically comes with a fineness of .999 or three nines (e.g. George the Victorious and Chinese Gold Panda coins) or .9999 or four nines (e.g. Canadian Gold Maple Leaf and American Buffalo coins). The gold market accepts bullion with fineness only up to .9999.
Other measures of purity were in use earlier in the 19th century, such as karat or carat. Now the term is used only in the jewelry market. The standard gold bar used in international trade is the 400 troy-ounce (12.44 kilogram; 438.9-ounces) Good Delivery gold bar. It comes with a fineness of .995.
Gold jewelry is made with fineness in the range of .585 and .999, while machine-made gold jewelry comes with purity in the range of .333 and .750. The rest of the alloy is made up of copper, silver, iridium, and/or tungsten that gives the alloy different characteristics such as color, malleability, and hardness in comparison with that of pure gold.
The purest bullion gold ever made was refined by Perth Mint in 1958 and it had a fineness of .999999 (six nines). Now, the purest gold bar available in the market is the special edition of Canadian Maple Leaf, which comes with a fineness of .99999 (five nines).
Fine gold has a fineness of .999 (three nines) and is called 24 karat.
Fineness can be written in different ways.
Commonly available fineness in gold are
- 9 (four nines fine)
- 999 (three nines fine) (24 karat)
- 995 (minimum fineness for Good Delivery gold bar)
- 990 (two nines fine)
- 3 (23 karat)
- 916 (22 karat)
- 833 (20 karat)
- 750 (18 karat)
- 625 (15 karat)
- 585 (14 karat)
- 417 (10 karat)
- 375 (9 karat)
- 333 (8 karat)
The minimum fineness for gold varies by country. In the US, 417 or 10 karat is legally the minimum permitted fineness in gold, while some European countries like the UK and France have set 375 or 9 karat as the minimum fineness to be called gold. In some countries like Germany, Denmark, and Greece, 333 or 8 karat is the legal minimum fineness.