Platinum group
Platinum 850
850‰
Cool silver-white, same visual appearance as higher-purity platinum. Cobalt alloy offers slightly improved springiness
Composition
85% platinum + 15% cobalt, iridium, or palladium
Physical properties
| Density | 19.50 g/cm³ | Weight per unit volume. Platinum is ~40% heavier than 18k gold at equal size |
|---|---|---|
| Melting range | 1650–1720 °C | Working temperature for alloys. Pure metals have a sharp melting point |
| Vickers hardness | 120 HV | Higher HV = greater scratch resistance in service |
| Mohs hardness | 4 | Approximate equivalent for comparative reference |
| Tensile strength | 430 MPa | Resistance to breaking under tension, relevant for prongs and fine settings |
| Purity | 85.00% | Fine metal content by mass |
| Tarnish resistance | Excellent | Surface oxidation / sulphidation under typical wear conditions |
| Workability | Good | Ease of forming, soldering, and fabricating under standard jewellery workshop conditions |
| Hypoallergenic | Hypoallergenic | Likelihood of triggering skin reactions under normal wear |
Common uses
Japanese and Asian-market jewellery, spring components, clasps where higher springiness is needed
Hallmarking & identification
Stamped 850Pt or PT850. Predominant in Japanese fine jewellery. Less common in European and US markets where 950 is standard.
Care & maintenance
Same care as 950 platinum. Long-lasting, tarnish-free. Develops natural patina over years of wear.
Market & pricing
Less expensive than 950 by weight due to lower platinum content. Comparable fabrication costs.