Quality checks

A box of coins

Every year, officials from the Royal Mint carry boxes of coins to Goldsmiths' Hall in the City of London. Inside are coins set aside during the previous year's minting, normally more than 50,000 of them, one from every batch of each denomination. A jury of goldsmiths, sitting as a formal court of law, then tests them.

This is the Trial of the Pyx, named after the Latin for a small box, and its first recorded public trial was in 1248, when twelve citizens of London and twelve goldsmiths were chosen to examine the money. The principle has not changed in nearly eight centuries: whoever makes a thing of value should not be the only one who checks it. Jewellery works the same way, with a jeweller's own checks at the bench and independent testing behind them.

Looking closely

Most checks start with good light and magnification. A jeweller's loupe is the classic tool, and 10x is the standard: GIA, for example, grades diamond clarity as seen by a skilled grader under 10-power magnification. Many faults that matter, a hairline gap in a jump ring, a lifted claw, a thin patch of plating, are close to invisible without one.

There is no single official checklist for jewellery workmanship. What follows are the checks that jewellers' own references and trade bodies most often describe, and where a recognised standard or test exists, it is named.

Size and dimensions

The simplest check is also one of the most important: is the piece the size that was ordered? Chains are measured for length, rings checked on a ring mandrel, pendants and charms measured with callipers. A necklace a few centimetres short sits in a completely different place on the body, which is why length matters so much (see Necklace lengths: a complete guide).

Clasps and jump rings

A necklace or bracelet hangs from its smallest parts: the clasp and the rings that join it to the chain. A jump ring, the little loop that joins a clasp or pendant to a chain, is only as secure as its join.

• Open rings are opened sideways. Suppliers' guidance is to twist the ends apart, not pull them open, because pulling a ring apart leaves it misshapen and weak.
• Ends meet flush. When closed, the two ends should sit tight against each other, with no gap for a fine chain to slip through.
• Soldered rings close the gap for good. Soldering a jump ring shut is the final step in securing it. Where a ring carries weight or takes strain, a soldered ring removes the gap altogether.
• Clasps open, close and hold. Each clasp should be worked by hand. Clasp type matters too: magnetic clasps, for example, are described by suppliers as less secure for heavier jewellery.

More on the choices in Clasp types explained.

Stone settings

A loose stone is the fault nobody notices until it has gone. In a claw or prong setting, each claw is cut with a small seat, called a bearing, that should fit the stone closely. Benchmarks published with GIA put it simply: there should be no gaps in any bearing, because any gaps will allow the stone to move or loosen. Claws should be even, and the stone should sit level.

Under a loupe, a jeweller checks that every claw is in contact with the stone and that nothing rocks. Assay offices also offer laboratory checks here: Birmingham Assay Office lists a stone adhesion test among its services, to check that stones are securely set.

Finish, plating and spelling

The surface gets its own look: edges smooth with no burrs to catch skin or clothing, no file marks or scratches left under the shine, and an even colour on plated pieces with no bare or dull patches, particularly in recesses and on the inside of loops where plating is thinnest. Plating thickness itself cannot be judged by eye, but it can be measured: assay offices use XRF to verify the thickness and composition of plated layers.

Personalised pieces add one more check, and it is the one no machine will do: reading the name, initials or date on the piece back against the order, letter by letter. A spelling mistake in metal cannot be polished out.

Testing the metal

You can't tell gold or silver content by sight or touch, which is the whole reason hallmarking exists. Testing is done in three main ways.

In practice the two work together. Sheffield Assay Office explains that pieces are routinely tested by XRF, but fire assay remains the reference method used to verify the results.

Hallmarking: the independent check

For precious metals, the UK has the strongest quality check of all built into law. It is an offence for a business to describe an unhallmarked piece as gold, silver, platinum or palladium, unless it is under the exemption weight. And a hallmark can only be applied after the piece has been tested by one of the four UK assay offices. Unlike every other check in this guide, it is done by someone other than the maker.

A hallmark tells you the metal content and who sent the piece for testing. The guides to the story of the hallmark and gold hallmarks explain how to read one.

Nickel, lead and cadmium

Some checks are about safety rather than looks, and here the law sets the standard. UK REACH, the chemicals law, limits three substances in jewellery.

The current version of the nickel test is BS EN 1811:2023, which replaced the 2011 edition. It simulates how much nickel a piece releases, which is what the law limits, rather than measuring how much nickel the metal contains. Testing is destructive and needs more than one piece: the London Assay Office says the British Standard method requires three articles to prove compliance. UK assay offices offer nickel, lead and cadmium testing, so this, too, can be independent.

Back to the box

The coins in the pyx are tested because a promise about metal is easy to make and hard to check. A piece of jewellery makes several promises at once: the size, the metal, the stone that will stay put, the clasp that will hold, the name spelled right. Some of them a jeweller checks with a loupe and a steady hand. The rest are checked by a laboratory, or by a jury of goldsmiths, which is as it should be.