Alloying Metal
Also: Additive metal, Secondary metal, Alloying agent
An alloying metal is a base or noble metal added to a precious metal in a defined quantity in order to deliberately alter hardness, colour, melting behaviour or other properties.
An alloying metal (also called an additive metal or alloying agent) is the portion of a precious metal alloy that does not consist of the precious metal itself. Without alloying metals, many applications would barely be possible: pure gold (999.9 ‰) is so soft it can be scratched with a fingernail — only the addition of other metals gives jewellery or coins the necessary hardness for everyday use. The fineness always indicates how much precious metal — and therefore how little alloying metal — is present in an alloy.
Which metals are used?
| Alloying metal | Typical use | Effect |
|---|---|---|
| Copper | Rose gold, sterling silver, 585 gold | Hardness ↑, reddish colour |
| Silver | Yellow gold, white gold base alloys | Lighter colour, ductility |
| Palladium | White gold (hypoallergenic) | White colour, tarnishing ↓ |
| Nickel | Older white gold | White colour (allergy potential) |
| Zinc | Solder alloys, yellow gold | Melting point ↓, hardening |
| Iridium / Ruthenium | Platinum alloys | Hardness ↑ in platinum |
Effect on material value
The melt value of a piece of jewellery is based exclusively on the fine weight of the precious metal, not on the weight of the alloying metals. For a 585 gold ring with a gross weight of 10 g, only 5.85 g of fine gold are relevant for valuation — the remaining 4.15 g of alloying metal (often copper and silver) barely contribute to the assessment. The exact material value can be calculated with the Melt Value Calculator.
Fine weight = Gross weight × (Fineness ÷ 1000)
Example 585 gold, 10 g: 10 × 0.585 = 5.85 g fine gold
Colour effects through alloying metals
The colour of a gold alloy depends directly on the proportion of alloying metals:
- Red gold / rose gold: high copper content (e.g. 750 ‰ gold + ~200 ‰ copper + ~50 ‰ silver)
- White gold: palladium (hypoallergenic) or historically nickel replaces copper entirely
- Green gold (electrum): high silver content, little or no copper
Tarnishing and allergy risk
Copper and nickel as alloying metals can trigger contact allergies in sensitive wearers. Nickel is strictly regulated in the EU for jewellery, piercing jewellery and skin-contact articles — the original Nickel Directive 94/27/EC was replaced and further tightened by REACH Regulation (EC) No 1907/2006, Annex XVII Entry 27. Palladium is considered a more compatible alternative. Silver develops a dark tarnish layer from sulphur compounds in the air — the alloying metal copper accelerates this process.
Key takeaway
The alloying metal determines the colour, hardness, allergy risk and tarnishing behaviour of a precious metal alloy, but has no material influence on the precious metal value — the only factor that matters is the fineness of the precious metal.