Gold doré and bullion:from the mine to thevault.

Most gold mines do not produce pure gold. They pour doré: a semi-pure alloy of gold and silver with small amounts of other metals. Doré bars vary widely in composition from one operation to another, and they cannot be sold as investment gold until they have been refined.

Refining takes place at specialised refineries, which assay the incoming doré, separate the gold from the silver and impurities, and cast bars, kilobars or grain of a stated fineness. Bars from refiners that appear on recognised accreditation lists are accepted by bullion dealers and markets around the world, which is why the refiner's mark matters.

A refinery's acceptance of doré or recycled material depends on two things: the assay and the documents. Under the OECD Due Diligence Guidance and the responsible-sourcing standards refiners commonly follow, they must know who the supplier is, where the material comes from and how it travelled, and they decline material whose provenance cannot be documented.

Recycled gold, from jewellery scrap, sweeps and electronic residues, follows the same path: it is melted, sampled and assayed before refining, and the same documentary standards apply.

Silver and the platinum-group metals follow similar logic. Silver is recovered from doré and base-metal refining, while platinum, palladium and rhodium come from PGM concentrates and, increasingly, from recycled autocatalysts.