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Ounce Gram
Gold £1218.96 £39.191
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Updated 01:50 09/03/21

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Gold purity


Pure gold is extremely soft and malleable. It is because of this that manufacturers, typically jewellers, often mix or alloy pure gold with other harder base metals. Without knowing a gold article’s precious metal content it is difficult to arrive at a true valuation.

To quantify this there are two major systems that measure purity. They are carat (karat in the US), and fineness. Both carat and fineness give figures that indicate the proportion of pure gold to other base metals in gold jewellery and products.
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Gold carat
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Carat expresses the proportion of gold to other metals in parts of 24. In this system, 24-carat is pure gold. 9-carat is nine-parts gold: the remaining fifteen parts of the 24 being composed of other metals.
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Gold fineness
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Fineness, in gold, silver and other precious metals, expresses the percentage of gold to other metals in parts per thousand. It is therefore a more precise scale than carat. In this system, 999.9 is pure gold. 9-carat gold, nine parts gold to fifteen parts other metals, is .375 fineness.

In the UK, with the exception of coins and pure gold bars, any manufactured gold products weighing over 1 gram or 0.0321507 troy ounce must be hallmarked with the item's fineness.

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UK carat and fineness

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How many carats is pure gold?
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Both 24-carat and 999.9 fineness are generally accepted as 100% pure gold. Despite this, in truth it is impossible to produce 100% pure gold. This is why, in common terms, pure gold is 999 or 999.9 not 1,000 fineness.

The most pure gold ever was made in 1957 by Australia's Perth Mint. This was 999.999 fineness, known as 'six nines fineness'. It has since been used by the Royal Mint as its benchmark for purity.

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Gold bars

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995 fineness is the minimum allowed purity for gold investment bars and is used as raw material for further gold alloying. The London Bullion Market Association undertakes gold testing and produces a 'Good Delivery List' that specifies standards for gold investment bars, which includes the required fineness.

All BullionByPost, bars are pure 24-carat gold and manufactured by refiners approved by the London Bullion Market Association. Investment gold is VAT-free and BullionByPost prices include FREE fully insured delivery on orders over £250.
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Minimum purity
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Generally, when describing items as gold, we are in truth referring to gold alloys. There are limits at which items, such as jewellery, contain so little gold they can no longer be called gold.

This minimum gold content varies by country. In the US, 10 carat or .417 fineness is the legal minimum. In France, the UK, Austria, Portugal and Ireland, 9-carat or .375 fineness is the minimum that can be called gold. In Denmark, Germany and Greece it is even lower at 8-carat or .333 fineness.

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List of common gold purities.