Measuring the Purity of Gold and
The Gold and silver market value is determined partly by purity. Logically, purer gold or silver mean a higher value. But how do we determine purity percentage, and how do we classify gold and silver that way?
The Millesimal fineness
There is a system of gold, silver and platinum purity denoting called Millesimal fineness. In this system the purity of precious metals are denoted by parts per thousand of pure metal by mass in the alloy. For example an alloy containing 80 percent gold will be denoted as ’’800’’. Some European countries use decimal hallmark stamps like ’’750’’, or ’’800’’, and markings like ’20K’, ’22K’, or anything else with ’K’ is commonly used in USA and Great Britain. This system is just an extension of the well-known karat (or carat) system, which denotes precious metal purity in karats.
The purity of gold and silver can be determined by experienced professionals and assayers , although there are methods you can try at home, for instance rubbing your gold over a porcelain plate, using acid tests or buying electronic testers to determine if your gold is real or not.
Understanding the numbers that denote purity
The precise purity of precious metals can be assessed only by using professional means. Gold purity can be expressed in millesimal fineness, which refers to the gold content in 1.000 parts of a bar. For example, a bar marked as ’’995 fineness’’ is 995 parts gold and 5 parts other metals, impurities, etc. The purest type of gold that can be found in the market is 999.9, also known as ’’four nines gold’’. Nines are not formal, but are a frequently used method of assessing the purity of gold and other precious metals. A gold sample is one nine or one-nine-fine if it is 900 fine, or 90 percent pure.
Some common karat denotations you will find are: 24 karat gold – 99.9 % pure gold (jewelry is not usually made with this high karat weight except in Asian, Indian or Middle Eastern countries, because it is very soft). It can mainly be found in bars and coins. Then we have 18 karat gold or 75 % gold mixed with other metals (sometimes mixed with palladium or silver). Further, we’ve got 14 karat gold or 58.5 % gold. The smallest karat denotation that is usually used for jewellery is 9 karat gold, or 37.5%.
Gold purity classification :
999.99 – the purest type of gold currently produced
999.9 – the purest gold that can be found on market
999 – 24 karats, fine gold
916 – 22 karats
833 – 20 karats
750 – 18 karats
625 – 15 karats
585 – 14 karats
417 – 10 karats
375 – 9 karats
Silver items are commonly 92.5 % pure ( sterling silver), with the remaining 7.5 % consisting of copper (this refers to US specifically). For example, if you wish to call an item ’’silver’’ in the USA, it must contain at least 92.5 % silver, but some items made of silver can contain different percentages depending on the country of origin. Sterling silver jewellery is usually plated with a thin coat of 99.9 % pure silver, to give it a shiny glow.
Silver purity classification :
999.9 – ultra fine silver
999 – fine silver (pure silver three nines fine)
958 – Britannia Silver
950 – French 1st Standard, Mexican silver
925 – Sterling silver
900 – Coin silver one nine fine
830 – Scandinavian silver
800 – German silver, Egyptian silver
By Lisa Casagrande | https://www.goldbullionaustralia.com.au