Purity of the Metal
The purity of gold is measured in Carats. The term Carat was used hundreds of years ago in the Middle East and is an important factor in buying gold as it indicates how pure the metal is.
The Carat
The carat is a measurement that tells you how many parts of gold and how many parts of other metal are in the gold alloy. For example your 24 Carat gold is considered to be 999.999 parts per thousand. One carat is one part of 24, or 41.66 parts of a thousand.
Now you may understand the basis that there can never be a total and absolute purity of gold. Your 22 Carat gold is 22/24th (gold is 916.000 parts per thousand and other metals have 84 parts). Your 18 Carat gold is 18/24th (gold is 750 parts per thousand and other metals have 250 parts). Similarly your 14 Carat gold is 14/24th or 585.000 parts per thousand and other metals have 415 parts. Your 9 Carat has this ratio: 9/24th (gold is 375.000 parts per thousand and other metals have 625 parts). This system of calculation gives only the weight of pure gold contained in an alloy.
| 24 carat gold | 99+ | 990 |
| 22 carat gold | 91.6 | 916 |
| 18 carat gold | 75.0 | 750 |
| 14 carat gold | 58.5 | 585 |
| 9 carat gold | 37.5 | 375 |
An alternative method of expressing purity is ‘fineness’. This expresses the purity of gold in parts per 1000.
Jewelry Grade Gold
Gold is usually alloyed with other metals such as silver, copper, zinc or silicon to produce purities less than 24 carat. Silver and copper and most commonly used alloying elements for gold. Pure gold is too soft to be able to be used for jewelry.
