Platinum 950
950‰, the jewellery standard
Cool, neutral white. Naturally white metal that never requires replating; develops a satin patina over time known as 'platinum patina'
Composition
95% platinum + 5% iridium, ruthenium, or cobalt depending on application
Physical properties
| Density | 21.10 g/cm³ | Weight per unit volume. Platinum is ~40% heavier than 18k gold at equal size |
|---|---|---|
| Melting range | 1700–1770 °C | Working temperature for alloys. Pure metals have a sharp melting point |
| Vickers hardness | 135 HV | Higher HV = greater scratch resistance in service |
| Mohs hardness | 4.3 | Approximate equivalent for comparative reference |
| Tensile strength | 450 MPa | Resistance to breaking under tension, relevant for prongs and fine settings |
| Purity | 95.00% | 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
High-end engagement rings, investment jewellery, watch cases, settings for important gemstones, heirloom pieces
Hallmarking & identification
Stamped 950Pt, PT950, or simply 950. Never replated; the white colour is inherent. Extremely dense: a platinum ring is approximately 40% heavier than an identical 18k gold ring.
Extremely durable and tarnish-resistant. Metal does not wear away but displaces; surface develops a satin 'patina' over time. Professionally polishable. Ultrasonic cleaning is generally safe.
Market & pricing
Typically 2–4× the price of 18k gold by weight due to rarity and density. Considered the prestige choice for important jewellery.