Gold alloys
9k Gold
9 karats, 375‰
Very pale yellow, the lightest of the standard gold karats. Can appear nearly champagne in some alloys
Composition
37.5% gold, 62.5% silver, copper, zinc, and other base metals
Physical properties
| Density | 11.00 g/cm³ | Weight per unit volume. Platinum is ~40% heavier than 18k gold at equal size |
|---|---|---|
| Melting range | 770–790 °C | Working temperature for alloys. Pure metals have a sharp melting point |
| Vickers hardness | 185 HV | Higher HV = greater scratch resistance in service |
| Mohs hardness | 3.5 | Approximate equivalent for comparative reference |
| Tensile strength | 430 MPa | Resistance to breaking under tension, relevant for prongs and fine settings |
| Purity | 37.50% | Fine metal content by mass |
| Tarnish resistance | Moderate | Surface oxidation / sulphidation under typical wear conditions |
| Workability | Excellent | Ease of forming, soldering, and fabricating under standard jewellery workshop conditions |
| Hypoallergenic | Allergy risk | Likelihood of triggering skin reactions under normal wear |
Common uses
UK and Australian high-street jewellery, fashion jewellery, affordable everyday pieces, children's jewellery
Hallmarking & identification
Common in UK, Australia, and Ireland. Stamped 375. Not considered gold in the US or most of Continental Europe. The legal minimum in the UK.
Care & maintenance
More prone to tarnishing than higher-karat alloys. Clean regularly. Avoid contact with perfume, lotions, and chlorine. May darken or discolour with prolonged exposure to chemicals.
Market & pricing
Most affordable gold karat. Popular UK and Australian entry-level fine jewellery price point.