When we think about gold bars or bricks, the image below is probably the type we all picture in our minds. There is only one standard size and weight of a gold brick for the London Bullion market Association (LBMA). But, did you know that this standard has some variations?
The London Bullion market Association (LBMA) sets standards for the makeup (purity and weight) for gold bars. A "standard"gold bar weighs approximately 400 troy ounces and has a minimum fineness of 995 parts per 1,000 pure gold (99.5% purity).
The standard unit of gold bullion settlement is the London Good Delivery Bar. Physical transaction of a London gold trade requires gold bar(s) conforming to the following specifications:
- minimum gold content: 350 fine ounces (approximately 10.9 kilograms)
- maximum gold content:430 fine ounces (approximately 13.4 kilograms)
- The gross weight of a bar should be expressed in ounces troy, in multiples of 0.025, rounded down to the nearest 0.025 of an ounce troy (see LBMA paper on "Weighing, Packing and Delivery Procedures for Gold and Silver Bars" at Annex D).
- The minimum acceptable fineness is 995 parts per thousand fine gold.
- Serial number
- Assay stamp of Acceptable Refiner
- Year of manufacture (expressed in four digits)
- Marks should be stamped on the larger surface (normally the cast surface at the top of the mould) of the two main surfaces of the bar.
- Bars should be of good appearance, free from surface cavities and other irregularities, layering and excessive shrinkage.
- They must be easy to handle and convenient to stack.
- Bar size, content and purity
The bar making process makes it difficult to produce bars of consistently accurate weight, so the LBMA does not impose a narrow range of bar weights and instead specifies the 350 to 430 ounce range described above. But most bars are much closer to 400 ounces than this range implies.
The specification is very demanding on purity and actual bar weight, because it is the fine gold content that is paid for - impurities come for free! So a bar's weight - however far removed from 400 oz - is multiplied by the purity to give the actual fine gold content.