In this guide (5 sections)
The three tests at a glance
| XRF | Touchstone + acid | Fire assay | |
|---|---|---|---|
| Damage | None | Scratch on item | Item is melted |
| Time | ~30 seconds | 2–5 minutes | Hours |
| Result | Exact % for each metal | Estimated karat range | Exact %, reference standard |
| Can you see it? | Yes, on screen | Rarely | No, done in a lab |
| Used by | Hallmarking centres, bullion traders, modern buyers | Traditional jewellers | Refineries, assay labs |
How XRF works
An XRF analyser beams X-rays at the surface of the gold. Each metal (gold, silver, copper, zinc) responds with its own fluorescence signature, which the analyser converts into percentages. The test is non-destructive, so your jewellery is unchanged.
Where XRF can be fooled
XRF reads the surface layer. A thick gold plating over silver or a filled bangle can show a high gold reading. Experienced valuers watch for warning signs — unusual weight for the size, worn edges showing a different colour, or a hollow sound — and combine XRF with density checks before pricing.
Why touchstone testing can cost you money
On a touchstone, the jeweller rubs the item on a dark stone and compares the streak against reference needles after applying acid. The result is a judgement call by eye. If the tester calls your 22K piece "about 20K", you lose roughly 9% of its value — and you cannot verify the call.
What we use
Every home visit includes purity testing and weighing in front of you, with every number shown before any price is discussed.
FAQs
Is XRF testing safe?
Yes. The analyser emits low-level X-rays only during the few seconds of measurement and is designed for handheld use.
Can I ask for my jewellery not to be scratched?
Yes. With XRF there is no need to scratch it at all.