18k White Gold
18 karats, 750ÔÇ░
Silvery white. The natural alloy has a faint yellow cast; final appearance depends on rhodium plating applied after fabrication
Composition
75% gold + 25% palladium (premium, hypoallergenic) or 75% gold + nickelÔÇôzincÔÇôcopper blend (standard)
Physical properties
| Density | 15.00 g/cm³ | Weight per unit volume. Platinum is ~40% heavier than 18k gold at equal size |
|---|---|---|
| Melting range | 1000–1100 °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 | 3 | Approximate equivalent for comparative reference |
| Tensile strength | 500 MPa | Resistance to breaking under tension, relevant for prongs and fine settings |
| Purity | 75.00% | Fine metal content by mass |
| Tarnish resistance | Excellent | Surface oxidation / sulphidation under typical wear conditions |
| Workability | Excellent | Ease of forming, soldering, and fabricating under standard jewellery workshop conditions |
| Hypoallergenic | Partial risk | Likelihood of triggering skin reactions under normal wear |
Common uses
Diamond rings, white metal settings, contemporary fine jewellery, engagement rings
Hallmarking & identification
Same 750 hallmark as yellow and rose gold. Colour is determined by alloy composition only, not by the mark. Rhodium plating is a finishing step, not part of the alloy.
Rhodium plating wears through over 1ÔÇô3 years of daily wear. Replating restores bright white colour. Avoid ultrasonic cleaners on plated pieces. Palladium-alloy variants are naturally white and need no replating.
Market & pricing
Palladium-alloy white gold carries a significant premium over yellow gold. Nickel-alloy versions are less expensive but may cause allergic reactions in sensitive wearers.