24ct gold is pure but soft. In order to make precious metals (Platinum, Gold, Palladium and Silver) strong enough to be workable, durable and wearable, they are alloyed with other metals.

In order to make sure the percentages of precious metals in the blend are true, an independent authority checks that each item is made of the right mix of metals and then stamps the piece with a hallmark to confirm the fineness of the metal. There are four Assay Offices in the UK, I use the The Goldsmiths’ Company Assay Office in London, which began hallmarking in 1327!

Any item of gold jewellery weighing over one gram has to be legally hallmarked in order to sell. Any lighter than 1g, and the piece is normally too tiny to stamp or laser engrave a hallmark on!

A hallmark:

• Consists of a series of marks applied to articles of the precious metals platinum, gold, palladium and silver

• Means that the article has been independently tested

• Guarantees that it conforms to all legal standards of purity (fineness)

• Guarantees provenance by telling us, as a minimum legal requirement, where the piece was hallmarked, what the article is made from, and who sent the article for hallmarking. 

The image below of a gold hallmark from the Assay Office website shows the Full Traditional Mark on 18ct gold. From left to right:

• Sponsor's Mark - Mine reads EAU

• Traditional Fineness - the crown is for gold

• Millesimal Fineness - this shows that at least 750 parts out of 1000 parts are pure gold

• Assay Office - the leopard denotes it was hallmarked in the London Office

• Date Letter - this shows it was hallmarked in 2015

The Silver hallmark below shows the Lion for Sterling Silver, the 925 shows that at least 925 parts out of 1000 are made of pure silver. The leopard shows it was hallmarked in London and the R shows it was hallmarked in 2016.

Use your phone camera to zoom in on the Hallmarks on a piece of jewellery you own - what can you see?

There are different hallmarking rules and symbols depending on where in the world a piece of jewellery was hallmarked.