XRF gold testing

Process photograph used for illustration.

What does XRF measure?

X-ray fluorescence identifies elements in the region of the item exposed to the instrument. Precious-metal analysers can report an estimate of gold and other detected metals at the tested surface. Suitability depends on the instrument, calibration, material and preparation.

When is it useful?

XRF can be useful for screening jewellery, coins and suitable metal surfaces without consuming a fire-assay sample. A measurement is local to the area tested; it does not automatically describe a whole bar or mixed lot.

Important limits to discuss

• Plating and surface treatments can affect interpretation.
• Different areas, solder joints and mixed materials may give different readings.
• An intact surface may not represent the interior.
• An ore sample needs a method and preparation suited to its matrix and expected concentration.

Questions to ask a Nairobi laboratory

Ask which instrument and calibration will be used, how many points will be tested, whether preparation is required and whether that preparation could mark the item. Request a report that identifies the sample, method and limits of the interpretation.

When should I discuss fire assay?

If the decision requires a representative gold determination, discuss an agreed sampling plan and appropriate laboratory assay. Taking a sample requires consent; confirm how much material will be consumed and what will be returned.

Understand fire assay and representative sampling →