Weight, Purity and Bullion Forms
A bullion product's description tells you which metal it contains, how much it weighs and how pure it is. Learn to read those details before comparing bars, coins or stored metal.
Grams and troy ounces
Precious metals are commonly measured in grams or troy ounces. One troy ounce equals approximately 31.1035 grams. It is heavier than the ordinary ounce sometimes used for everyday goods, so the two should not be confused.
A product may be described in grams, kilograms or fractions of a troy ounce. Convert products to the same unit when you want to compare the amount of metal they contain.
What does purity mean?
Purity, also called fineness, is the proportion of a product's metal content that is the named precious metal. It may be expressed as a percentage or as parts per thousand.
999
999 fineness means 999 parts out of 1,000 are the named metal. That is 99.9% purity.
999.9
999.9 parts out of 1,000 corresponds to 99.99% purity.
22 carat gold
A 22 carat gold product contains approximately 22 parts gold out of 24. Its total weight and fine gold content are different.
Total weight vs fine metal content
Total weight includes every metal in a product. Fine metal content is the amount of pure gold, silver or platinum within it. This distinction matters most when a product is not nearly pure.
Example: If a product has a total weight of 10 grams and a fineness of 999, it contains 10 × 0.999 = 9.99 grams of the named precious metal. Always check whether an advertised weight refers to total weight or fine metal content.
Bars, coins and other forms
Bullion is commonly available as cast bars, minted bars and investment coins. Products can differ in size, purity, manufacturer, finish and packaging. Some coins also carry a legal tender denomination, but their metal content and market price are separate from that face value.
A collectible coin may command a price influenced by its rarity or design. Jewellery prices can include craftsmanship and gemstones. Neither price should be assumed to represent only the value of the precious metal inside.
What do marks and certificates tell you?
A bullion product may show its manufacturer or mint, metal type, weight, fineness and identifying marks. Packaging or a certificate may supply additional details. Check those details against the seller's product description and keep a record of your purchase.
LBMA Good Delivery refers to particular standards for large wholesale gold and silver bars. A small retail bar made by a refiner on an accredited list is not, simply by its size or brand, itself a London Good Delivery bar.
What should you compare?
Start with the metal, fine metal content, purity and product form. Then compare the full buying price and the amount you could receive when selling. The next lesson explains why a physical product's price can differ from the spot market quote.