What is an assay of precious metal?
By Jared James · Last updated 21 May 2026
Definition
An assay is the formal testing of a precious metal to determine how much pure gold, silver, platinum or palladium it actually contains. It is carried out by an assay office, which is an authorised independent body, and involves analysing a small sample of the metal against the claimed purity. Once a piece passes, the assay office strikes it with a hallmark confirming the metal and its standard. In Britain and Australia, hallmarking and assaying have a long legal history protecting buyers from misrepresented metal quality.
Frequently asked questions
- What is the difference between an assay and a hallmark?
- An assay is the testing process that checks the metal's purity. The hallmark is the set of stamps applied to the piece after it passes, confirming what the assay found. One leads to the other: the assay is the test, the hallmark is the result.
- Who carries out an assay?
- Assay offices are independent authorised bodies. The UK has four traditional assay offices in London, Birmingham, Sheffield and Edinburgh. Australia does not have a mandatory hallmarking system, so pieces sold here may carry UK or European hallmarks if they were assayed there.
- Can you assay jewellery you already own?
- Yes. You can send a piece to an assay office or have a jeweller use a touchstone test or acid test to give a rough indication of purity. For a precise result, fire assay or XRF analysis by a qualified lab is the reliable method.
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