Reading a raw gold doré assay without being fooled
Updated
SHORT ANSWER
Read a gold doré assay by checking three things before the number: the method (fire assay is the settlement reference, XRF is only a surface screen), how the sample was taken and sealed, and which independent laboratory issued the result.
Key takeaways
- A purity figure without a method is not a specification.
- Fire assay settles value; XRF only screens.
- Jointly witnessed, split and sealed samples prevent disputes.
Method first
Fire assay remains the reference for gold content; XRF is a fast surface screen, not a settlement basis. Ask which one produced the number.
Sample discipline
Drill or melt samples taken under joint supervision, split and sealed, protect both sides from a disputed result.
Questions buyers ask next
- What is the difference between doré and refined gold?
- Doré is a semi-refined alloy of gold, silver and minor metals poured at or near the mine. Refined gold has been processed to a declared fineness by a refinery.
- Why can two labs report different purity?
- Doré is not perfectly uniform, so sampling point and method matter. Contracts set a tolerance and an umpire laboratory for that reason.
- Who chooses the laboratory?
- Buyer and seller agree it in the contract before inspection, together with the split-sample and umpire procedure.