Gold, Understanding Its Carats

Gold is an amazing material, not only for its warmth and brilliance but for the remarkable properties that make it so enduring. In fine jewellery, the term “carat” (or “karat” in some regions) expresses the purity of gold, how many parts of a piece’s metal composition are pure gold versus other elements that enhance its strength, hue, and wearability.

What Does “Carat” Mean?
Pure gold is 24 carats, meaning it consists entirely of gold atoms. However, pure gold is soft and malleable, unsuitable for daily wear. To strengthen it, gold is alloyed with other metals such as silver, copper, or palladium.

The carat value reflects this ratio:

18ct gold - 18 parts gold to 6 parts alloy (75% pure gold)

14ct gold – 14 parts gold to 10 parts alloy (58.5% pure gold)
9ct gold – 9 parts gold to 15 parts alloy (37.5% pure gold)


The Origins of the Gold Carat
The concept of the carat dates back to ancient Greece, where merchants used the carob seed (Ceratonia siliqua) as a standard of weight due to its uniform size. The Greek term kerátion evolved through Arabic and Italian before entering English as carat. By the Middle Ages, gold purity was expressed in a 24-part system, a measure of how much of a metal was pure gold. Pure gold proved too soft for coins, leading to the addition of other metals for strength. This gave rise to the 24-carat purity scale still used today.

Carat or Karat?
In the UK and Australia, jewellers use the term carat (ct). In the United States, the spelling karat (K or kt) became standard to distinguish gold purity from gemstone carats.


18ct Gold (75% Pure Gold)
18ct gold embodies the perfect mix of material purity and performance. With three-quarters pure gold, it glows with a rich, buttery warmth while maintaining exceptional strength.

From a scientific perspective, 18ct gold’s high gold content makes the it the most chemically inert, meaning it is extremely resistant to tarnishing or corroding. Its balance of durability and malleability makes it ideal for fine heirloom jewellery designed to last generations.

At Shimell and Madden, we craft our delicate drawn-wire rings exclusively in 18ct gold, a metal perfect for fine detail yet strong enough to endure daily wear.

14ct Gold (58.5% Pure Gold)
14ct gold offers a modern equilibrium of beauty and practicality. Its tone is slightly softer and lighter than 18ct gold, making it especially flattering on fairer skin tones.

The addition of copper and silver creates a tighter atomic structure, which makes it a more scratch resistant, but slightly more brittle compare to 18ct. This makes 14ct gold ideal for necklaces, earrings, and everyday heavier pieces.

Popular in Europe and the US, 14ct gold is increasingly appreciated in the UK for its subtle tone.

9ct Gold (37.5% Pure Gold)
Containing just over a third pure gold, 9ct is often chosen for its accessibility and warm tone. However, from a metallurgical view, it behaves quite differently from higher carat alloys. Its higher copper content gives it a distinctive rosy hue, but also alters its crystalline structure, increasing brittleness while reducing overall resilience.

Though 9ct gold is frequently marketed as the “harder” metal, this is a misconception. Hardness and durability are not synonymous: while 9ct may resist surface scratching slightly better, it is more prone to stress fractures and metal erosion over time. This is supported by empirical data, on the Vickers hardness scale, which measures metal resistance to deformation, 9ct gold typically scores between 80 and 120, depending on its alloy composition and condition. By contrast, 18ct gold ranges from 135 to 165, indicating a more balanced structure with superior toughness and longevity.

For this reason, we recommend 9ct gold for ear studs, pendants, and occasional-wear pieces, jewellery that celebrates the warmth of gold without enduring constant wear. For rings or heirloom-quality designs, however, the greater structural integrity of 18ct gold ensures beauty that truly lasts a lifetime.

22ct Gold (91.7% Pure Gold)
22ct gold glows with a deep, amber-orange tone, rich in tradition and heritage. However, its high gold content means it remains soft and pliable, unsuitable for intricate or lightweight pieces.It is most often used in ornamental or ceremonial jewellery, where its luxurious colour and cultural significance outweigh its softness. A celebration of gold in its near-purest form.

Hallmarking: The Assurance of Authenticity
In the United Kingdom, hallmarking is both a legal requirement and a heritage practice. Every piece we create is independently tested and hallmarked to verify its gold purity and fineness. Your hallmark is your guarantee of authenticity, integrity, and craftsmanship.

Choosing Your Ideal Carat
We have picked carats to reflect the usage of the jewellery, whether occasional or everyday while being considerate of budget. How we make the jewellery also plays a part into the metal that we choose to use. If you would like more information the best choice for you and what style we can offer in different carats please get in touch.