Pd500 Palladium — The 500-Parts-Per-Thousand Hallmarkable Alloy
Pd500 Palladium — The 500-Parts-Per-Thousand Hallmarkable Alloy
Britain's lower-fineness palladium standard, harder and cheaper than Pd950 but cosmetically and structurally compromised
Pd500 is a palladium alloy containing 500 parts per thousand of pure palladium — that is, 50 per cent palladium by weight — with the balance made up of base or precious metals chosen for hardness, colour, and workability, typically silver, copper, or ruthenium. It is the lower of the two palladium fineness standards recognised by the British hallmarking system since palladium became a hallmarkable precious metal in 2009; the higher standard is Pd950. Pd500 occupies a small share of the market for hallmarked palladium jewellery, used principally in budget items and in industrial applications where its hardness is more useful than its lustre.
Composition and properties
Half-palladium alloys are noticeably greyer in tone than the higher-fineness standards, with a duller surface that does not take as bright a polish. Hardness rises substantially as the palladium fraction is reduced; Pd500 is harder than Pd950 and considerably harder than pure palladium, making it more resistant to scratching but also more difficult to work and re-finish. Density is lower than Pd950, around 11 grams per cubic centimetre depending on alloying metals, and the alloy is correspondingly lighter on the wearer than platinum or higher-fineness palladium.
Tarnish resistance is reduced relative to Pd950: copper-bearing variants in particular can show oxidation under prolonged skin contact, while silver-bearing variants are more dimensionally stable but cosmetically duller. The alloy is generally hypoallergenic, particularly when copper content is low, but should not be assumed allergen-free for sensitive wearers without composition disclosure from the manufacturer.
Hallmarking
The UK Hallmarking Act 1973, as amended in 2009 to add palladium as a hallmarkable precious metal, recognises four palladium fineness standards: 500, 950, 999, and a less commonly used 999.5. Articles over one gram are required to be assayed and hallmarked at one of the four UK assay offices — London, Birmingham, Sheffield, or Edinburgh — before they can be described or sold as palladium. The Pd500 hallmark consists of the sponsor's mark, the fineness mark 500, the palladium symbol (three overlapping ellipses), the assay office mark, and the date letter. Items below the one-gram threshold may be sold without a full hallmark.
Trade position
Pd500 has not displaced Pd950 in fine palladium jewellery and remains a niche choice. The greyer tone, lower corrosion resistance, and modest cost saving relative to the much higher-fineness Pd950 do not in most cases justify the cosmetic compromise for buyers willing to consider palladium as a precious-metal alternative to platinum. Where Pd500 does appear, it is most often in mass-market wedding bands and in items where weight savings or hardness are valued over surface finish.
In the trade
Buyers should expect Pd950 to be the default palladium standard in fine jewellery and should treat Pd500 as a budget-tier specification. Verification by hallmark inspection or by XRF analysis is straightforward; the fineness mark 500 alongside the palladium symbol is unambiguous. Resizing and refinishing of Pd500 should be undertaken by jewellers familiar with the alloy's hardness, which can complicate hand-engraving and traditional bench work.