When you buy platinum jewelry, you might notice small markings like 950 Pt or 900 Pt engraved inside the band. These stamps reveal the purity of your metal. Let’s decode how platinum is graded and how it compares to gold karats.
How Platinum Purity Is Measured
Unlike gold (measured in karats), platinum purity is expressed as parts per thousand.
| Stamp | Purity | Meaning |
|---|---|---|
| 950 Pt | 95% | The most common and premium grade of platinum jewelry |
| 900 Pt | 90% | Slightly lower purity; durable for high-stress settings |
| 850 Pt | 85% | Seen in vintage or certain regional standards |
| 999 Pt | 99.9% | Ultra-pure; typical for bullion/bars, not everyday jewelry |
Common Platinum Alloys
- 950 Pt/Ru — with ruthenium: bright white, high wear resistance.
- 950 Pt/Ir — with iridium: slightly softer; great for intricate settings.
- 900 Pt/Co — with cobalt: very strong; may be slightly magnetic.
All remain naturally white and hypoallergenic; alloy choice affects hardness, polish, and workability.
Platinum vs. Gold Purity
| Metal | Common Purity | % Precious Metal | Notation |
|---|---|---|---|
| Platinum | 950 Pt | 95% | Numeric stamp (e.g., 950 Pt) |
| Gold | 18K | 75% | Karat system |
| Gold | 14K | 58.5% | Karat system |
In purity terms, 950 Pt is roughly comparable to high-karat gold (≈23K) — platinum jewelry is usually crafted at higher fineness.
International Standards & Hallmarks
- UK/EU: Assay office hallmark + numeric fineness (e.g., 950) with “Pt/Plat”.
- USA: “Platinum/Plat” usually denotes ≥95% Pt; alloys labeled like “Pt900/Ir”.
- Japan: 850 Pt and 900 Pt are widely accepted standards.
Identifying Authentic Platinum
- Look for a clear hallmark: 950 Pt, 900 Pt, etc.
- Platinum feels dense and does not yellow over time.
- Prefer documented pieces with reputable certification.
Related Reading
- Start with our overview: Understanding Platinum: The Most Prestigious Precious Metal
- Compare with gold grades: Understanding Gold Hallmarks: 24K, 22K, 18K, 14K
Conclusion
Platinum purity stamps — 950 Pt, 900 Pt, 850 Pt — are your shortcut to authenticity and durability. Knowing these marks helps you choose pieces that hold their beauty and value for life.