Almost everyone who invests in physical gold or silver might have this question. How are the weight an purity of the precious metals measured? The weight of gold and silver items is sometimes given in either kilograms or grams. The official unit of measure for precious metals is however the troy ounce. One troy ounce (oz) equals 31.1034768 grams. Do not mix the Troy ounce of English ounce (28.34g).
The purity of gold and silver is measured in fineness. Ultimately fineness is the ratio to other metals in the product. The fineness indicates the purity of the metal in parts per thousand.
For example, a 1 oz Canadian maple leaf gold coin has a fineness of 0.9999, which means that the coin is made of 99.99% pure gold. Therefore, the coin actually weighs 31.1065875 grams, which means 31.1065875 x 0.9999 = 31.1034768. Say. 1 oz of 100% pure gold.
Another example is the 1 oz South African Krugerrand Investment Gold Coin, which has a gross weight of 33.93 grams and a fineness of 916.7, which is equivalent to 91.67% purity, which means that 33.93 x 0.9167 = 31.1034768 and thus 1 oz of 100% pure gold.
In addition to fineness, the traditional unit of purity for gold is the carat (K). The highest carat is 24, which is at least 99.9% pure gold. The purity of European jewelry is often 14 or 18 carats, which is 14/24 = 58.3% and 18/24 = 75% pure gold.
Carat is often used to describe the purity of jewelry, where fineness is clearly most advantageous for investment gold, but is also often used in jewelry.
Therefore the question of how the weight and purity of precious metals are measured can be a tricky one.