Gold Jewellery Guide: 9ct, 14ct, 18ct and 22ct Explained
The World's Most Treasured Metal
Gold has captivated humanity for over 6,000 years. Prized for its beauty, rarity and resistance to corrosion, it remains the foundation of fine jewellery worldwide. But when you walk into a jeweller's and see "9ct", "14ct", "18ct" and "22ct" on the labels, what do these numbers actually mean — and which should you choose?
At Sterling Diamond in Burlington Arcade, Mayfair, we work primarily with 18ct gold and platinum, but we believe an informed client is the best client. This guide explains everything you need to know about gold purity, colour and quality.
Understanding Gold Purity
The Carat System
Gold purity is measured in carats (abbreviated "ct" in the UK, "K" or "kt" in the US). Pure gold is 24 carats. Because pure gold is too soft for most jewellery, it is alloyed with other metals to increase hardness and durability. The carat number tells you what fraction of the alloy is pure gold.
Gold Purity Comparison Table
| Carat | Gold Content | Millesimal Fineness | UK Hallmark | Characteristics |
|---|---|---|---|---|
| 9ct | 37.5% | 375 | 375 | Hardest and most durable. Palest gold colour. Most affordable. |
| 14ct | 58.5% | 585 | 585 | Good balance of durability and colour. Popular internationally. |
| 18ct | 75.0% | 750 | 750 | Rich colour, excellent durability. The standard for fine jewellery. |
| 22ct | 91.7% | 916 | 916 | Deep, warm colour. Softer — best for plain bands and traditional designs. |
| 24ct | 99.9% | 999 | 999 | Pure gold. Too soft for most jewellery. Used for investment bars and coins. |
What Makes Up the Other Percentage?
The non-gold portion of the alloy typically includes:
- Silver — softens the colour, improves workability
- Copper — adds strength and warmth (creates rose gold)
- Zinc — improves casting properties
- Palladium — creates white gold, adds hardness
- Nickel — historically used in white gold (now largely replaced due to allergies)
Gold Colours Explained
Yellow Gold
The classic. Yellow gold's warm hue comes from alloying pure gold with silver and copper. The higher the carat, the richer and deeper the yellow colour.
- 9ct yellow gold — a pale, subtle yellow
- 18ct yellow gold — a rich, warm yellow that most people picture when they think of gold
- 22ct yellow gold — a deep, almost orange-tinged yellow
Best for: Classic engagement rings, wedding bands, pendants, earrings. Yellow gold complements warmer skin tones and pairs beautifully with diamonds of G–J colour.
White Gold
White gold is created by alloying gold with white metals — typically palladium, silver and zinc. The resulting alloy has a greyish-white appearance and is almost always rhodium-plated to achieve a bright, silvery-white finish.
Important to know: Rhodium plating wears over time (typically 12–18 months with daily wear) and needs periodic re-application. At Sterling Diamond, we offer complimentary rhodium re-plating for pieces purchased from us.
Best for: Contemporary engagement rings, diamond jewellery (the white metal makes diamonds appear brighter), and those who prefer a silver-toned look with the prestige of gold.
Rose Gold
Rose gold's romantic blush tone comes from a higher proportion of copper in the alloy. The more copper, the pinker the gold.
- 9ct rose gold — a pronounced pink colour (more copper relative to gold)
- 18ct rose gold — a subtle, warm pink that is extremely flattering on most skin tones
Rose gold does not require rhodium plating and develops a beautiful patina over time.
Best for: Vintage-inspired designs, stackable rings, and anyone who wants something distinctive. Rose gold has been one of the most popular choices at our Burlington Arcade showroom in recent years.
Hallmarking in the United Kingdom
What Is a Hallmark?
In the UK, it is a legal requirement to hallmark any gold item weighing more than 1 gram before it can be described as gold and offered for sale. The hallmark is your guarantee of metal purity.
The Four Components of a UK Hallmark
- Sponsor's mark — identifies the manufacturer or retailer (e.g., Sterling Diamond's registered mark)
- Fineness mark — the millesimal fineness (375, 585, 750 or 916)
- Assay office mark — identifies which assay office tested the metal (London's mark is a leopard's head)
- Date letter (optional since 1999) — identifies the year of hallmarking
The London Assay Office
All Sterling Diamond pieces are hallmarked at the London Assay Office at Goldsmiths' Hall — the same institution that has been testing precious metals since 1327. The London leopard's head hallmark is recognised worldwide as a mark of quality and authenticity.
Durability Comparison
| Property | 9ct | 14ct | 18ct | 22ct |
|---|---|---|---|---|
| Hardness | Hardest | Hard | Medium | Soft |
| Scratch resistance | Excellent | Very good | Good | Fair |
| Tarnish resistance | Fair | Good | Very good | Excellent |
| Hypoallergenic | No (may contain nickel) | Usually | Yes (palladium-based alloys) | Yes |
| Suitable for daily wear | Yes | Yes | Yes | With care |
| Suitable for gem setting | Yes | Yes | Yes (preferred) | Limited |
Price Comparison
Gold jewellery pricing depends on three factors: the gold content, the weight of the piece, and the craftsmanship involved. As a rough guide:
| Carat | Relative Gold Cost | Typical Use |
|---|---|---|
| 9ct | Baseline | Fashion jewellery, children's jewellery, everyday pieces |
| 14ct | ~1.5x 9ct | Mid-range jewellery, popular in the US and Europe |
| 18ct | ~2x 9ct | Fine jewellery, engagement rings, luxury pieces |
| 22ct | ~2.5x 9ct | Traditional Asian jewellery, plain wedding bands |
Note: The craftsmanship and design of a piece often represent a larger proportion of the price than the raw metal cost, particularly for bespoke and designer pieces.
Which Gold Should You Choose?
For Engagement Rings and Fine Jewellery
We recommend 18ct gold or platinum. The 75% gold content provides a rich, luxurious colour while offering sufficient hardness for secure gemstone settings. 18ct gold is the international standard for fine jewellery and holds its value well.
For Wedding Bands
18ct gold is our standard recommendation. For those who prefer a deeper gold colour and a softer feel, 22ct is a beautiful option for plain bands. For maximum durability (particularly for those who work with their hands), platinum or 9ct gold may be more practical.
For Everyday Jewellery
9ct or 14ct gold offers excellent durability at a more accessible price point. These lower carats are ideal for pieces that will endure daily wear and tear — chains, bracelets and hoop earrings.
For Investment
22ct and 24ct gold have the highest intrinsic metal value. However, for jewellery that combines wearability with investment value, 18ct gold from a reputable maker offers the best of both worlds.
Caring for Gold Jewellery
- Clean regularly with warm soapy water and a soft brush
- Remove before swimming (chlorine can damage alloys), exercising and applying cosmetics
- Store separately to prevent scratching — gold is softer than most people realise
- Re-plate white gold every 12–18 months to maintain its bright finish
- Professional service annually — we check settings, clean ultrasonically and polish
Visit Sterling Diamond
Our Burlington Arcade showroom in the heart of Mayfair showcases jewellery in 18ct yellow, white and rose gold, as well as platinum. Our specialists can help you understand the differences in person and choose the perfect metal for your piece.
Sterling Diamond — Burlington Arcade, Mayfair, London W1J 0QJ
