Affinage / Refining
Also: Refining, Precious metal refining, Parting
Affinage denotes the industrial cleaning and processing of raw precious metals to trade- or investment-grade fineness.
Affinage (from the French affiner – to refine) is the technical heart of precious metal processing: it converts impure raw metal – such as doré bars straight from the mine or melted-down scrap gold – into trade-ready metal with a defined fineness. Only through refining do precious metals become exchange-tradable and meet international standards such as the LBMA Good Delivery rules.
Where Does the Raw Metal Come From?
Refineries process two fundamentally different material streams:
- Primary raw metal – doré bars from gold mines (typically 70–95% Au/Ag content), platinum-ore concentrates or nickel sludges from which platinum-group metals are extracted.
- Secondary raw metal – scrap gold, scrap silver, dental gold alloys, electronic scrap (urban mining) and industrial returns from catalytic-converter processing.
Common Processes at a Glance
| Process | Metal | Principle | Fineness reached |
|---|---|---|---|
| Chlorination (Miller) | Gold | Cl₂ gas displaces impurities | ~995‰ |
| Electrolysis (Wohlwill) | Gold | Anodic dissolution, cathodic deposition | 999.9‰ |
| Electrolytic silver refining | Silver | Silver-nitrate bath, cathode 999+‰ | 999‰ |
| Solvent extraction / ion exchange | Platinum-group metals | Selective precipitation from hydrochloric solution | 999.5‰ |
| Fire refining | Gold/silver | Oxidising melt, slag removal | 980–990‰ (preliminary stage) |
The Wohlwill Process (Gold, Simplified)
Anode (raw gold, ~995‰)
→ dissolution in HCl/HAuCl₄ electrolyte
→ cathodic deposition as fine gold 999.9‰
The process is energy-intensive but delivers the purest commercially produced gold and forms the basis for fine gold bars and investment coins.
From the Refinery to the Tradable Bar
An accredited refinery – such as Heraeus, Umicore, PAMP Suisse or Argor-Heraeus – goes through several quality-assurance steps after refining:
- Sampling and assay: precise determination of the fineness before and after refining.
- Casting or minting: refined metal is processed into cast or minted bars.
- Stamping: manufacturer, weight, fineness and serial number are applied (hallmark).
- Certification: LBMA-listed refineries are subject to regular audits; their Good Delivery stamp is the global quality mark.
With the melt value calculator, you can quickly determine the metal value of an object before delivering it to a refinery – useful guidance when comparing purchase offers.
Economic Significance
A region's refining capacity is an indicator of its standing in the global precious metals market. Switzerland (Valcambi, Argor-Heraeus, PAMP Suisse) is estimated to process 70% of the world's secondary gold stream. The UK, with the London bullion market at its centre, and Germany, with Heraeus (Hanau) and C. Hafner (Pforzheim), are also important locations.
For private investors, affinage is especially relevant in scrap gold recovery: the purchase price depends on the fineness – knowing it means negotiating better. Keeping an eye on the current gold price as a reference helps to assess offers realistically. The same applies to silver.
In Brief
Affinage is the process that transforms raw or mixed precious metal into the exchange-tradable, standard-compliant metal that ends up in bars and coins. Without a functioning refining infrastructure, neither standardised investment products nor a liquid world market would be possible.