999 Gold

999 gold is considered the best purity of gold readily available, and is described as being 24 carat. This refers to purity in parts per 1,000 – known as fineness – meaning 999 parts are gold.

Pure gold is soft and malleable, making it impractical for many applications. When used to make jewellery for example, it would quickly become damaged under the wear and tear of everyday use. Gold is therefore mixed with other harder metals to make a gold alloy, and could be mixed with other precious metals or base metals.

Pure 999 gold is used either as a raw material for alloying, or for investment gold bullion coins and 24ct gold bars which will be less handled.

A collection of 999 gold bars and coins - all available in our store.

Gold is one of the most expensive precious metals. As such, when valuing items, it is important to know the proportion of pure gold contained in the item. If something is made from 999 gold, then the full value of gold can be assured.

There are three units of gold content measurement that are commonly used. The least used of these is as a simple percentage – in the case of 999 gold this would be 99.9% pure.

Traditionally, the purity of gold to other metal was given as parts of 24 – the system of carats that many of us know. In the United States it is spelt karat. Pure, 100% gold is 24 carat (24 karat gold). Based on this maths, 50% gold then would be 12 carat or 500 gold.

The third measurement type is known as fineness. Traditional carat measurement is slowly being replaced with a more precise millesimal fineness scale, meaning it uses parts per 1,000 rather than 24. This is where 999 gold takes its name from.

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999.9 gold

It is currently impossible to refine gold to a purity of 100% – 1,000 fineness. 999.999 fineness is the purest gold ever produced, and proved too expensive to be a regular occurrence. 13 troy ounces of 999.999 gold were refined by Australia’s Perth Mint in 1957.

Generally, the closest to 100% pure gold that refiners are able to reach in everyday production is a fineness of 999.9 gold. It should be noted however that anything at or above 999 gold is still considered pure, and would fetch the same price when selling it back to dealer such as BullionByPost, and 999.9 gold offers an additional but a fractional increase to the level of purity.

The British Royal Mint, the Royal Canadian Mint, and the Perth Mint all strike their gold coins to this purity of 999.9 gold, and proudly display it on their coins (as seen below). This makes 999.9 gold one of the most commonly seen purities for bullion coins and bars.

The table below shows some of the various common gold alloy amounts:

Carat	Fineness	Percentage
24	999.99	100%
22	916	91.6%
18	750	75%
15	625	62.5%
14	585	58.5%
10	417	41.7%
9	375	37.5%
8	333	33.3%