XRF vs fire assay: choosing a gold test
Which test should you discuss?
XRF measures elemental composition near a tested surface. Fire assay determines gold in a prepared test portion and consumes material. The right approach depends on the material, the sampling plan and the decision the result needs to support.
Confirm method suitability and availability directly with your laboratory.
Compare the methods
| Consideration | XRF screening | Fire assay |
|---|---|---|
| What it describes | Elements at a tested surface region. | Gold in the prepared test portion. |
| Effect on the item | Measurement can leave the item intact, although preparation may mark it. | The test portion is consumed. |
| Main question to ask | Does the tested surface represent the material of interest? | Does the selected sample represent the intended bar or lot? |
| Useful context | Instrument, calibration, test points, surface condition and limitations. | Sample selection, preparation, analytical finish, units and reporting basis. |
If the item must stay intact
Explain that constraint before testing. Ask whether XRF screening and suitable complementary checks answer your question without sampling. A surface result alone does not establish that an item's interior has the same composition. Do not authorise filing, cutting or drilling without understanding the effect on the item.
If the result will support a purchase
Agree the testing and reporting requirements with the parties before submitting material. Ask how the sample connects to the original lot, who may witness weighing and sampling, and whether a retained split is appropriate. A laboratory should select the method rather than treating a quick scan and a representative assay as interchangeable products.
If you have ore or concentrate
Describe the matrix, mass and preparation history. Discuss representative preparation and a gold assay suited to the expected concentration. A reading from an isolated rock surface does not describe the grade of a whole lot.
Comparing quotes fairly
Ask for preparation, sample count, method, report and turnaround in the quotation. A cheaper test can answer a narrower question. Compare the scope of the result alongside its price; there is no verified price list for the requested service yet.
Five questions before choosing
- What exactly do I need to establish?
- What material will the test actually describe?
- Is destructive preparation allowed?
- Who needs to accept the report?
- What remains unverified after the test?