Fineness
Also: Purity, Fine gold content, Carat
Fineness indicates how much pure precious metal is contained in an alloy – expressed in parts per thousand (e.g. 999) or in carats (e.g. 585 = 14 carat).
Fineness – also called purity – describes the proportion of pure precious metal in an alloy. Pure precious metals are too soft for many purposes, so they are mixed with other metals (such as copper, silver or palladium). Fineness states how high the proportion of the actual precious metal is in this mixture.
Two notations: parts per thousand and carat
There are two common ways of expressing fineness:
- Parts per thousand (‰): 999 means 999 of 1000 parts are fine gold – i.e. 99.9%. This figure appears today on almost all bars and bullion coins.
- Carat (for gold): here 24 carat = 100% fine gold. 18 carat corresponds to 18/24 = 750/1000.
The most important gold alloys at a glance:
| Carat | Fineness | Fine gold content |
|---|---|---|
| 24 ct | 999 | 99.9% |
| 22 ct | 916 | 91.6% |
| 18 ct | 750 | 75.0% |
| 14 ct | 585 | 58.5% |
| 9 ct | 375 | 37.5% |
| 8 ct | 333 | 33.3% |
Why fineness determines the value
The material value of a piece of jewellery depends directly on its fineness. A 585 gold ring contains only 58.5% fine gold – the rest is copper and silver, which contribute little to the precious-metal value. To calculate the pure metal value (the melt value), you multiply the weight by the fineness and the current gold price. This is exactly what the melt value calculator does automatically – even for mixed lots of 333, 585 and 750 gold.
Fineness stamp (hallmark)
In the UK, precious-metal articles above certain weight thresholds must be tested and struck with a legally required hallmark that certifies the fineness – for example "750" for 18-carat gold or "925" for sterling silver. UK hallmarking is compulsory under the Hallmarking Act 1973 and administered by the Assay Offices; the stated fineness must be truthful. With dental gold a hallmark is usually absent altogether; here the specialised dental gold calculator helps, assuming typical alloys between 750 and 900.
In brief
Fineness is the key to material value: without it, no reliable value can be derived from weight and daily price. Anyone wanting to value jewellery or broken gold should always determine the fineness first – via the hallmark or an expert test.