Pt-Ru Alloy
Pt-Ru Alloy
Platinum-ruthenium, the workshop standard for Pt950
Pt-Ru alloy is a platinum-ruthenium formulation widely used in Pt950 jewellery production, valued for its balanced combination of hardness, workability, and cost. Ruthenium content typically ranges from 3 to 5 per cent, with Pt950Ru (95% platinum, 5% ruthenium) the most common industry standard formulation across the United States, the United Kingdom, and most Western markets.
Properties
Ruthenium is a platinum-group metal with high hardness, a high melting point, and good corrosion resistance. Adding 3 to 5 per cent to platinum produces an alloy harder than pure platinum and harder than Pt-Pd, but more workable and less expensive than Pt-Ir. The alloy retains platinum's white colour and tarnish resistance and exhibits good casting and forming properties for general jewellery production. Specific gravity is close to that of pure platinum.
In the workshop
Pt-Ru is the alloy most workshops reach for when fabricating Pt950 jewellery in conventional designs: solitaire shanks, three-stone settings, halo mountings, wedding bands, and general fabrication work. The alloy casts well, rolls and draws cleanly, and finishes to the high polish that platinum jewellery demands. Soldering and welding are straightforward at standard platinum temperatures. The hardness is sufficient for most prong and bezel applications, though for the most demanding high-wear settings on very valuable stones some workshops still prefer Pt-Ir for its additional springiness.
In the trade
Pt950Ru is the dominant Pt950 formulation in the principal Western platinum jewellery markets. The alloy is recognised under all major hallmarking regimes — UK Assay Office, US Federal Trade Commission, and continental European authorities — and is the default expectation when a piece is described as Pt950 without further specification. For wedding bands and engagement rings, Pt-Ru is the standard against which other platinum alloys are compared.