Additive Metal / Alloying Metal
Also: Additive Metal, Admixture Metal, Alloying Element
An alloying metal is a base or precious metal blended into a precious metal in a measured amount to deliberately shape its hardness, colour, melting behaviour or other characteristics.
Within any precious-metal alloy, the share that is not the precious metal itself goes by the name alloying metal (also additive metal or alloying element). Take these additions away and a great many uses would fall apart: fine gold at 999.9 ‰ is soft enough to mark with a fingernail — it is only by mixing in other metals that a coin or a piece of jewellery gains the working hardness it needs. The fineness figure always tells you how much precious metal an alloy holds — and, by the same token, how little alloying metal.
The metals that get used
| Alloying metal | Typical use | Effect |
|---|---|---|
| Copper | Red gold, sterling silver, 585 gold | Hardness ↑, red colouring |
| Silver | Yellow gold, white gold base alloys | Lighter colour, ductility |
| Palladium | White gold (hypoallergenic) | White colouring, tarnishing ↓ |
| Nickel | Older white gold | White colouring (allergy potential) |
| Zinc | Solder alloys, yellow gold | Melting point ↓, hardening |
| Iridium / Ruthenium | Platinum alloys | Hardness ↑ in platinum |
Why it does not drive material value
A piece of jewellery's melt value rests solely on the fine weight of the precious metal — the mass of the alloying metals plays no part. Take a 585 gold ring weighing 10 g gross: only 5.85 g of fine gold counts arithmetically toward value, while the remaining 4.15 g of alloying metal (typically copper and silver) barely registers in the valuation. To nail down the precise material value, use the melt value calculator.
Fine weight = gross weight × (fineness ÷ 1000)
Example 585 gold, 10 g: 10 × 0.585 = 5.85 g fine gold
Colour born from the alloy
How the alloying metals are proportioned dictates the colour a gold alloy takes on:
- Red gold / rose gold: a lot of copper (for instance 750 ‰ gold + ~200 ‰ copper + ~50 ‰ silver)
- White gold: copper gives way entirely to palladium (hypoallergenic) or, historically, to nickel
- Green gold (electrum): heavy on silver, with little or no copper
Tarnish and the allergy question
For wearers with sensitive skin, copper and nickel used as alloying metals can set off contact allergies. Across the EU, nickel faces strict limits in jewellery, piercing jewellery and any article touching the skin — the original Nickel Directive 94/27/EC gave way to the REACH Regulation (EC) No. 1907/2006, Annex XVII entry 27, which tightened the rules further still. Palladium is generally seen as the gentler alternative. Silver, for its part, grows a dark tarnish film as airborne sulphur compounds attack it — a reaction that the alloying metal copper speeds along.
In brief
Colour, hardness, allergy risk and tarnishing behaviour of a precious-metal alloy are all set by the alloying metal — yet it barely moves the precious-metal value. There, the only thing that counts is the fineness of the precious metal.