Argentium silver is a proprietary silver alloy developed in the 1990s at the Art and Design Research Institute of Middlesex University in England by metallurgist Peter Johns. It replaces a portion of the copper present in conventional sterling silver with germanium, producing an alloy that is markedly more resistant to tarnish and firescale while retaining the bright white colour and workability prized in jewellery manufacture. Two commercial grades exist: Argentium 935, containing 93.5% silver, and Argentium 960, containing 96% silver — both exceeding the 92.5% silver threshold of standard sterling. The alloy is trademarked and hallmarked with a distinctive flying unicorn device alongside the fineness mark 935 or 960.

Composition and Metallurgy

Standard sterling silver (925) comprises 92.5% silver and 7.5% copper. The copper confers hardness and durability but is also responsible for two persistent problems: firescale, a reddish-purple cupric oxide bloom that forms beneath the surface during soldering or annealing, and tarnish, which results from copper sulphides forming at the surface on exposure to atmospheric sulphur compounds. Argentium addresses both by substituting germanium — typically 1.2% in the 935 grade — for a portion of the copper. Germanium migrates preferentially to the alloy's surface during heating, forming a thin, stable germanium oxide layer that acts as a barrier against both oxidation and sulphidation.

The practical consequences for the bench jeweller are significant. Firescale is effectively eliminated, removing the need for the anti-firescale flux coatings, pickle treatments, and surface depletion techniques that sterling demands. The alloy can also be precipitation hardened — heated to approximately 200–300 °C and held for a period — which increases hardness without cold-working, a process not available with conventional sterling. In its annealed state Argentium is somewhat softer and more ductile than sterling, facilitating forming and stone-setting; after heat hardening it achieves hardness comparable to, or exceeding, work-hardened sterling.

Tarnish Resistance

The germanium oxide surface layer confers genuine long-term tarnish resistance under normal wearing conditions, a claim supported by accelerated sulphur-atmosphere testing. This does not render Argentium entirely immune to tarnish — prolonged exposure to high-sulphur environments or certain skin chemistries can eventually discolour any silver alloy — but the resistance is substantially greater than that of sterling. For finished jewellery pieces intended for retail display or infrequent wear, the practical benefit is considerable: pieces maintain their polish and brightness with minimal maintenance.

Working Properties and Considerations

Argentium solders with conventional silver solders, though dedicated Argentium solders are available and preferred by many makers. The alloy is compatible with standard pickle solutions (dilute sulphuric or citric acid) and responds well to conventional polishing compounds. One notable characteristic is that Argentium work-hardens more slowly than sterling, which can be advantageous when extended forming is required but demands attention when spring-temper properties are needed in findings or clasps — heat hardening is then the recommended route to stiffness.

Fusion welding (using a laser or pulse-arc welder) is particularly effective with Argentium, as the reduced copper content lowers the tendency toward hot cracking at weld seams. This has made the alloy popular in production environments where laser welding is routine.

Hallmarking and Trade Recognition

In the United Kingdom, Argentium silver may be submitted to an assay office for hallmarking; the fineness marks 935 and 960 are recognised under the Hallmarking Act 1973 as amended. The flying unicorn trademark is applied by licence from the Argentium International organisation. In the United States, the alloy is recognised by the International Gem Society (IGS) and referenced in trade literature as a distinct category from sterling, though US hallmarking requirements differ from the UK's compulsory system. The higher fineness of Argentium 960 in particular positions it closer to Britannia silver (958) than to standard sterling.

Applications in Contemporary Jewellery

Argentium has been adopted by studio jewellers, small-batch manufacturers, and some larger production houses, particularly where tarnish-free presentation is a selling point and where the elimination of firescale reduces finishing labour. It is well suited to stone-set pieces where repeated heating cycles during manufacture would otherwise risk firescale contamination beneath collets or bezels. Its bright, white colour — slightly whiter in appearance than sterling owing to the higher silver content of the 960 grade — is also valued in designs where rhodium plating is undesirable and a natural silver surface is preferred.

Further Reading

• International Gem Society — Argentium Silver