Affinage / Refining
Also: Refining, Precious metal refining, Parting
Affinage refers to the industrial purification and processing of raw precious metals to tradeable or investment-grade fineness levels.
Affinage (from the French affiner – to refine) is the technical heart of precious metal processing: it transforms impure raw metal – such as dore 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-tradeable 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 – dore bars from gold mines (typically 70–95 % Au/Ag content), platinum ore concentrates or nickel sludges from which platinum group metals are recovered.
- Secondary raw metal – scrap gold, scrap silver, dental gold alloys, electronic scrap (urban mining) as well as industrial returns from catalytic converter processing.
Common Processes at a Glance
| Process | Metal | Principle | Achieved fineness |
|---|---|---|---|
| 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 melting, slag removal | 980–990 ‰ (pre-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 yields the purest commercially produced gold and forms the basis for fine gold bars and investment coins.
From the Refinery to a Tradeable Bar
An accredited refinery – such as Heraeus, Umicore, PAMP Suisse or Argor-Heraeus – runs through several quality assurance steps after refining:
- Sampling and assay: exact determination of 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 undergo regular audits; their Good Delivery stamp is the global mark of quality.
With the melt value calculator you can quickly determine the metal value of an object before submitting it to a refinery – a useful benchmark when comparing purchase offers.
Economic Significance
The refining capacity of a region is an indicator of its standing in the global precious metals market. Switzerland (Valcambi, Argor-Heraeus, PAMP Suisse) processes an estimated 70 % of the world's secondary gold stream. Germany, with Heraeus (Hanau) and C. Hafner (Pforzheim), is likewise a significant location.
For private investors, affinage is most relevant when recovering scrap gold: the purchase price depends on fineness – those who know it negotiate better. Keeping the current gold price in view as a reference helps to assess offers realistically. The same applies to silver.
In Brief
Affinage is the process that turns raw or mixed precious metal into the exchange-tradeable, standard-compliant metal that ends up in bars and coins. Without a functioning refining infrastructure, neither standardised investment products nor a liquid global market would be possible.