Refining / Affinage
Also: Affinage, Precious metal refining, Parting
Refining, or affinage, is the industrial purification of raw precious metals to the fineness levels required for trading and investment.
Refining — often called affinage, from the French affiner (to refine) — is the technical heart of the precious-metals supply chain. It converts impure raw metal, such as doré bars coming straight out of the mine or melted-down scrap gold, into trade-ready metal of a defined fineness. Only after refining do precious metals become exchange-tradable and capable of meeting international standards such as the LBMA Good Delivery rules.
Where does the raw metal come from?
Refineries handle two fundamentally different input streams:
- Primary raw metal — doré bars from gold mines (typically 70-95% Au/Ag), platinum ore concentrates, or nickel slimes from which platinum-group metals are recovered.
- Secondary raw metal — scrap gold, scrap silver, dental gold alloys, electronic waste (urban mining), and industrial returns from catalytic-converter processing.
The main processes at a glance
| Process | Metal | Principle | Fineness achieved |
|---|---|---|---|
| Chlorination (Miller) | Gold | Cl2 gas drives off impurities | ~995 per mille |
| Electrolysis (Wohlwill) | Gold | Anodic dissolution, cathodic deposition | 999.9 per mille |
| Electrolytic silver refining | Silver | Silver-nitrate bath, cathode 999+ | 999 per mille |
| Solvent extraction / ion exchange | Platinum-group metals | Selective precipitation from HCl solution | 999.5 per mille |
| Fire refining | Gold/silver | Oxidising melt, slag removal | 980-990 per mille (pre-stage) |
The Wohlwill process (gold, simplified)
Anode (raw gold, ~995 per mille)
-> dissolved in HCl/HAuCl4 electrolyte
-> cathodic deposition as fine gold 999.9 per mille
The process is energy-intensive but yields the purest commercially produced gold, forming the basis for fine-gold bars and investment coins.
From refinery to tradable bar
An accredited refinery — such as Heraeus, Umicore, PAMP Suisse, or Argor-Heraeus — runs several quality-assurance steps after refining:
- Sampling and assay: exact determination of fineness before and after refining.
- Casting or minting: refined metal is worked into cast bars 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 quality mark.
The melt-value calculator makes it quick to work out the metal value of an item before you hand it to a refinery — a sensible reference point when comparing purchase offers.
Economic significance
A region's refining capacity is a measure of its standing in the global precious-metals market. Switzerland (Valcambi, Argor-Heraeus, PAMP Suisse) is estimated to process around 70% of the world's secondary gold flow. Germany, with Heraeus (Hanau) and C. Hafner (Pforzheim), is another important hub.
For private investors, refining matters most in scrap-gold recovery: the buying price depends on fineness, so knowing it puts you in a stronger negotiating position. Keeping an eye on the current gold price as a reference helps you judge offers realistically. The same applies to silver.
In brief
Refining is the process that turns raw or mixed precious metal into the standard-compliant, exchange-tradable metal that ends up in bars and coins. Without a working refining infrastructure, neither standardised investment products nor a liquid world market would be possible.