XRF testing for precious metals
How X-ray fluorescence spectrometry works and why it's replacing acid tests.
At a glanceX-ray fluorescence spectrometry (XRF) has become the standard testing method for precious metals in buyback counters, jewelry stores, and control offices. It is non-destructive, fast (2-30 seconds) and very accurate.
Principle: An X-ray beam excites the atoms of the sample. Each element emits secondary X-rays at a characteristic energy, allowing identification and quantification of all elements present.
Precision: Portable devices (Thermo Fisher Niton, Olympus Vanta) offer accuracy of ±0.1-0.5% for gold. Desktop devices (Bruker S1 Titan) achieve ±0.05%. Sufficient for commerce, not for official certification.
Limitations: XRF analyzes the surface (5-50 microns deep). Thick plating can fool the device. For suspect pieces, a depth test (cut + analysis) or densimetric test is needed.
Cost: A portable XRF device costs CHF 25,000-45,000. A cantonal control office charges CHF 20-50 per analysis. For a jeweler handling regular buybacks, the investment is recouped in 6-12 months.
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