Jewelry Metal Marks Explained: 18K, PT950, 925 & AU750
When you look at an engagement ring or fine jewellery, you will often see small stamps such as 18K, AU750, PT950 or 925. These are metal purity marks (hallmarks). They tell you the exact percentage of pure metal in the alloy and are one of the most important quality indicators.
This guide explains the most common jewellery metal marks used in Hong Kong and internationally, so you can choose with confidence.
What Do Jewellery Metal Marks Mean?
Metal marks (also called fineness marks or hallmarks) show the purity of the precious metal. Because pure gold, platinum and silver are too soft for daily wear, they are mixed with other metals to create stronger alloys. The number tells you how much pure metal is present.
| Mark | Metal | Purity | Common Name |
|---|---|---|---|
| 18K / 750 / AU750 | Gold | 75% pure gold | 18 Karat Gold |
| 14K / 585 | Gold | 58.5% pure gold | 14 Karat Gold |
| PT950 / Pt950 | Platinum | 95% pure platinum | 950 Platinum |
| PT900 / Pt900 | Platinum | 90% pure platinum | 900 Platinum |
| 925 | Silver | 92.5% pure silver | Sterling Silver |
Gold Marks: 18K, 750 and AU750
18K (or 18 Karat) means the metal contains 75% pure gold. The remaining 25% is usually silver, copper or other metals that improve hardness and colour.
- 18K / 750 – the most popular standard for fine jewellery and engagement rings in Hong Kong and Asia
- AU750 – the European marking system (AU = gold, 750 = 750 parts per thousand)
- Both 18K and AU750 indicate the same purity
18K gold offers an excellent balance of colour, durability and value, which is why it is the preferred choice for most engagement rings.
Platinum Marks: PT950 and PT900
Platinum is naturally white, dense and highly durable. The two most common marks are:
- PT950 – 95% pure platinum (the higher and more popular standard in Hong Kong and Japan)
- PT900 – 90% pure platinum
PT950 feels heavier and more substantial on the finger. It does not require rhodium plating and develops a soft natural patina over time. Many buyers choose PT950 for engagement rings because of its purity and hypoallergenic properties.
Silver Mark: 925
925 (Sterling Silver) contains 92.5% pure silver. It is widely used for fashion jewellery and some everyday pieces. While beautiful, silver is softer than gold or platinum and can tarnish, so it is less common for high-end engagement rings that are worn daily.
Which Metal Should You Choose for an Engagement Ring?
| Metal | Best For | Key Advantages |
|---|---|---|
| 18K White Gold | Classic look, lighter feel | Bright white (with rhodium), more accessible price |
| PT950 Platinum | Long-term durability & purity | Naturally white, hypoallergenic, heavier feel |
| 18K Yellow / Rose Gold | Warm or romantic style | Rich colour, does not need plating |
In Hong Kong, both 18K white gold and PT950 platinum are widely accepted and trusted for engagement rings. The choice usually comes down to personal preference for weight, colour tone and maintenance.
How to Verify Metal Marks
- Look for the stamp on the inner side of the ring band
- Reputable jewellers in Hong Kong will clearly show the mark and explain it
- For high-value pieces, ask for a certificate or written confirmation of the metal content
Frequently Asked Questions
Is AU750 the same as 18K?
Yes. AU750 is the European way of writing 18K gold (75% pure gold).
Is PT950 better than 18K white gold?
Neither is universally “better”. PT950 is purer and denser; 18K white gold is lighter and often more affordable. Both are excellent for daily wear.
Does 925 silver work for an engagement ring?
It can be used, but most people prefer gold or platinum for long-term durability and prestige.
Will the metal mark affect the diamond?
No. The metal mark only describes the setting. Diamond quality is judged by the 4Cs and the certificate (GIA / IGI).
Start Choosing Your Setting
Whether you prefer the classic brightness of 18K gold or the substantial purity of PT950 platinum, understanding these marks helps you make a confident decision.
