Bullion refers to any form of gold whose value is based only on the quantity and quality present. This value is specified in terms of weight, Troy ounces, grams, or kilograms, and purity.
The International Organization for Standardization (ISO) has established a standard, ISO 4217, that defines three-letter codes and three digit numbers for currencies including gold bullion. Gold bullion's code is XAU and number is 959. By definition gold bullion, XAU, is expressed in US dollars per one Troy ounce of gold.
Coins, such as the gold bullion Krugerrand, are called bullion coins because it is only the gold content that is being valued. However, bullion coins do carry a premium because they are minted and are widely recognized.
Gold bullion bars are either cast or minted. Cast bars are normally produced directly from gold that has been melted. The traditional method is to pour molten gold into a mould. A modern method is to put gold granules or cut pieces of gold in a mould and melt them in a furnace.
Minted gold bullion bars are cut from a cast gold bar that has been rolled to a uniform thickness. The cutting is done with a die to create blanks that have the required dimensions and weight. The surfaces of minted gold bullion bars are smooth and even. Markings are applied by to the gold bullion bars buy a minting press. Minted gold bullion bars are manufactured in a variety of shapes and often incorporated in jewellery.
The gold industry and exchanges specify the types of gold bars they will accept. These gold bars are referred to as "good delivery" bars meaning they meet the required specifications for the particular industry use or exchange. For example, the London Bullion Market Association (LBMA) specifies good delivery gold bullion bars must be 400 ounces of 99.95% gold or better. The COMEX requires 100 ounce gold bullion bars of 99.95% gold or better.
Citation Gold Bars Worldwide