For thousands of years, gold has fascinated humankind for its unalterable brilliance, its geological rarity and its universal status as a store of value. And yet, when it comes to acquiring a precious creation or placing capital, one fundamental question returns again and again: should you choose 18-carat gold or 24-carat gold?
Although instinct often pushes us towards absolute purity, the metallurgical and jewellery-making reality is a good deal more subtle. Between mechanical strength, the demands of stone setting, chromatic nuance and taxation, each fineness answers a precise purpose.
Here is a full explanation from our master craftsmen and precious-metal experts, to guide you towards the best-informed choice.
Understanding the fundamental difference: purity and composition
To grasp the distinctions between the different types of gold, it helps first to understand the metrological system that governs this precious metal.
| Fineness | 24K gold (999‰) | 18K gold (750‰) |
|---|---|---|
| Composition | 99.9% pure | 75% pure + 25% alloy |
| Description | Fine, unalloyed gold | Gold + copper / silver / etc. |
What is a carat (K) in jewellery?
Historically inspired by the carob seed — renowned in antiquity for its remarkably constant weight — the metric carat (k or ct) measures the proportion of pure gold contained in a total mass divided into 24 parts.
In modern metrology and in international trade, the system of parts per thousand (‰) is progressively replacing the carat, offering absolute precision:
- 24 carats corresponds to 999/1000 (fine gold, a theoretical maximum purity of 99.99%).
- 18 carats corresponds to 750/1000 (that is, 750 parts of pure gold to 250 parts of other noble metals).
24-carat gold: the pure state (99.9%)
24K gold is the metal in its refined native state. Physically it is a remarkable element: unalterable, impervious to oxidation, entirely rust-proof, and possessed of a deeply saturated, sunlit yellow tone. On the Mohs scale, however, which measures the hardness of minerals from 1 to 10, pure gold scores only 2.5. Its malleability is extreme: simple pressure from a fingernail or a light knock is enough to scratch, nick or permanently deform it.
18-carat gold: the perfect balance (750 parts per thousand)
18-carat gold is the standard of excellence in French fine jewellery. Composed of 75% pure gold, it incorporates 25% of added metals (also called alloying metals) such as fine silver, copper or palladium. This carefully measured alloy gives the metal optimum structural rigidity without compromising either its prestige or its high precious-metal content.
The technical match: 18-carat gold versus 24-carat gold
| Material | Hardness (Mohs) | Assessment |
|---|---|---|
| 24K gold | 2.5 | Very soft |
| 18K gold | 3.5 | Robust |
| Platinum | 4.5 | Very hard |
| Diamond | 10.0 | Absolute hardness |
Durability and resistance: why 24K is not suited to everyday wear
Because of its intrinsic plasticity, a piece of 24-carat gold jewellery withstands neither repeated mechanical friction nor structural stress. Worn on the finger or the wrist, it quickly deforms under the simple force of everyday movement.
More critical still: 24-carat gold cannot hold precious stones securely. The claws retaining a diamond or an emerald would spread under slight tension, risking the irretrievable loss of the gem. 18-carat gold, by contrast, offers the ideal mechanical strength to pass through several generations without structural damage.
Aesthetics, colour and alloy nuances
While 24 carat exists only in its natural bright yellow, 18-carat gold allows master craftsmen to develop a refined chromatic palette through the precisely measured dosing of alloying metals:
- 18K yellow gold: 75% pure gold + 12.5% fine silver + 12.5% copper. A warm tone, faithful to antique gold.
- 18K white gold: 75% pure gold + silver + palladium, finished with rhodium plating for a mirror brilliance.
- 18K rose gold: 75% pure gold + 20% copper + 5% fine silver, giving powdery, warm reflections.
- Set out in the table below.
| Shade | Gold | Silver | Copper |
|---|---|---|---|
| Yellow gold | 75% | 12.5% | 12.5% |
| Rose gold | 75% | 5% | 20% |
| White gold | 75% | Silver / palladium | — |
On the markets, 24-carat gold follows the international price of the fine gold bullion (Au) directly. The price per gram of 18-carat gold represents, mathematically, 75% of the spot value of pure gold, to which is added the foundry work, the shaping and the stone setting of the finished piece.
Use: which fineness to choose for your purpose?
| Criterion | 24-carat gold (999/1000) | 18-carat gold (750/1000) |
|---|---|---|
| Pure gold content | 99.9% (24/24) | 75.0% (18/24) |
| Hardness (Mohs scale) | ~2.5 (very malleable, vulnerable to knocks) | ~3.5 to 4.0 (robust, resistant to wear) |
| Preferred use | Bars, small ingots, savings coins | Fine jewellery: rings, necklaces, bracelets |
| Scratch resistance | Low (marks under a fingernail) | High (ideal for continuous daily wear) |
| Stone setting | Not advised (risk of stones working loose) | Ideal (firm, lasting hold) |
| French state hallmark | Seahorse | Eagle's head |
| Colour range | A single saturated yellow | Classic yellow, rhodium-plated white, refined rose |
| Hypoallergenic properties | 100% hypoallergenic | Hypoallergenic (European nickel-free standards) |
1. For fine jewellery and pieces worn through life: the supremacy of 18 carat
For jewellery worn every day — rings, wedding bands, necklaces or bracelets — 18-carat gold is the essential standard of French and international fine jewellery. It guarantees flawless longevity, withstands moderate knocks, preserves the fineness of engraving and holds the most delicate pavé settings securely.
2. For pure investment and storing wealth: 24-carat gold
If your intention is purely financial — building a physical reserve of savings — 24-carat gold in the form of bars, small ingots or bullion coins is the most appropriate solution. In France and in the European Union, investment gold (purity of 995‰ or above) benefits from a favourable tax framework, notably an exemption from VAT on acquisition.
Expertise & trust: how to authenticate 18K and 24K gold
France applies some of the strictest regulations in the world on the control and guarantee of precious metals, administered by the Bureau de la Garantie and the customs service.
| Fineness | Official hallmark |
|---|---|
| 18-carat gold (750‰) | Eagle's head |
| 24-carat gold (999‰) | Seahorse |
- The fineness hallmark (state guarantee): 18-carat gold (750‰) is struck with the official eagle's head hallmark, compulsory in France for any gold article weighing more than 3 grams. 24-carat gold (999‰) is identified by the seahorse hallmark or by the direct "999" marking on sealed bars.
- The maker's mark: lozenge-shaped for French manufacturers, it attests to the traceability of the piece and to the workshop it came from.
- Laboratory testing: approved workshops and foundries carry out checks by X-ray fluorescence spectrometry or by the traditional method of cupellation, guaranteeing an exact fineness to the nearest part per thousand.
Frequently asked questions
How is the buy-back value of an 18-carat gold piece calculated?
It is calculated by multiplying its pure gold weight (weight × 75%) by the official rate of the day, less foundry costs.
Why are 9K and 14K gold not advised in fine jewellery?
Containing less than 59% pure gold, these alloys oxidise, darken in contact with the skin and rapidly lose their market value.
Why is 24-carat gold rare in French jewellery?
Too soft to hold stones securely or to resist everyday deformation, pure gold is reserved for savings — unlike 18K gold, which is made to last.
How do you clean an 18-carat gold piece at home?
Soak it for 10 minutes in warm soapy water, brush it gently with a very soft-bristled brush, then dry it with a chamois cloth.
The verdict: which is the better gold?
- To wear, to hand down and to mark a unique moment: 18-carat gold (750/1000) is unquestionably the better choice, technically and aesthetically. It combines the preciousness of authentic gold with the robustness needed for daily wear over a lifetime.
- To store wealth and secure your assets: 24-carat gold (999/1000) stands as the sovereign standard, in the form of small ingots and savings coins.
Salia Gold Paris: excellence in fine jewellery
At Salia Gold Paris, we believe that a precious piece should bring together aesthetic emotion, exceptional making and real, lasting value.
That is why all of our collections — rings, openwork necklaces, pendants, anklets and creations with heart, infinity, clover or bohemian-inspired motifs — are worked exclusively in 18-carat gold (750/1000), in keeping with the traditions of French fine jewellery.
✦ ATELIER SALIA GOLD PARIS — OUR COMMITMENTS ✦
✓ Certified 18-carat gold (750/1000 fineness)
✓ Jewellery making and precision in France
✓ Lifetime care, cleaning and resizing for our private clients
✓ Guaranteed buy-back according to gold weight and the rate of the day
Would you like to discover creations made to last a lifetime?
- Explore our catalogue online: discover our selections of minimalist, layerable jewellery in our official boutique.
- Visit us in Paris: come and see the brilliance of our pieces and enjoy the personal advice of our expert jewellers at Salia Gold Paris, 22 Rue Vignon, 75009 Paris, France. Telephone: +33 1 71 28 40 62.