Unfortunately, all that glitters is not gold - and even in the UK, there are rogue jewellers who misrepresent the metal content of their jewellery.

That’s where hallmarking comes in: your official guarantee that the gold, silver, platinum or palladium in your jewellery is exactly what it claims to be.

At The Diamond Store, every piece is independently hallmarked at the London Assay Office to certify its metal purity and authenticity. This ensures that when you buy from us, you’re investing in jewellery of verified quality - designed to last a lifetime.

We visited the London Assay Office, where it all happens, to bring you this guide (and video!) explaining why hallmarking remains one of the most trusted forms of consumer protection.

WATCH OUR HALLMARKING VIDEO HERE:

1. Hallmarking is the law in the UK

In Britain, any jewellery described or sold as gold, silver, platinum or palladium must be hallmarked under the Hallmarking Act 1973.

This law ensures that every precious metal item sold in the UK meets strict purity standards verified by an official Assay Office.

2. What is a hallmark?

A hallmark is an official Government seal stamped onto precious metal objects to certify their purity.

Testing the metal’s composition is called assaying, and it can only be performed by one of the UK’s four authorised Assay Offices.

A hallmark typically includes several marks:

• The Assay Office town mark (for example, a leopard’s head for London)
• The metal fineness mark (such as 750 for 18K gold)
• Optional marks such as a date letter or sponsor’s mark

3. A tradition over 700 years old

British hallmarking is one of the world’s oldest forms of consumer protection. The first Assay Office opened in London in 1327, and the same principles of trust and transparency still guide hallmarking today.

4. The UK’s four Assay Offices

All hallmarking in Britain is carried out by one of these four Government-authorised offices:

• London – leopard’s head
• Birmingham – anchor
• Sheffield – Yorkshire rose
• Edinburgh – castle

5. The precious metals that must be hallmarked

By law, gold, silver, platinum and palladium must all be hallmarked.

Each metal must meet a minimum level of purity:

• Gold is stamped according to karat (9K, 14K, 18K, 22K, etc.)
• Silver, platinum and palladium each have their own standard fineness marks

These marks ensure you know exactly what metal - and what quality - you are buying.

6. Hallmarking protects both consumers and jewellers

Because it’s impossible to tell a metal’s purity by eye, hallmarking provides essential reassurance. It guarantees that your jewellery is genuine, while also protecting ethical jewellers from competitors who might falsely market lower-quality metals as precious.

7. Modern technology meets traditional craftsmanship

At the Assay Offices, both modern and traditional methods are used to test precious metals.

Advanced tools such as x-ray fluorescence and laser analysis now work alongside centuries-old hand-stamping techniques to ensure precision and authenticity.

8. Only officially registered hallmarks can be used

Only jewellery carrying an officially registered British or international hallmark can legally be sold in the UK.

If you’re ever unsure, you can verify hallmark symbols through the International Association of Assay Offices or by visiting an Assay Office’s website.

9. The only exceptions: very lightweight items

Some small jewellery items are exempt from hallmarking due to their minimal metal content.

Hallmarking is not required for pieces under the following weights:

• Gold: 1 gram
• Platinum & palladium: 0.5 grams
• Silver: 7.78 grams

10. Misrepresenting a hallmark is a criminal offence

Under the Hallmarking Act, it’s illegal to claim that jewellery is gold, silver, platinum or palladium unless it bears a genuine hallmark.

It’s also a criminal offence to remove, alter, deface or counterfeit a hallmark.

In summary

Hallmarking remains one of the oldest - and most important - consumer protections in the jewellery industry.

When you buy from The Diamond Store, your hallmark is your guarantee of purity, authenticity and trust. Every piece is certified to ensure it’s made from genuine precious metal, responsibly crafted, and designed to last for generations.