When it comes to gold, "carats" describe the purity of the metal. But what does that actually mean? And why does the difference between caratages matter?
The carat system
The carat system expresses gold purity on a scale of 24. Pure gold is 24 carats (24K), meaning all 24 parts out of 24 are gold.
The most common caratages are:
- 24K (999.9): 99.99% pure gold — used for investment bars
- 22K (916): 91.6% gold — used for some investment coins (e.g. the Sovereign and the Krugerrand)
- 18K (750): 75% gold — the standard for jewellery in Italy
- 14K (585): 58.5% gold — common in jewellery from other countries
- 9K (375): 37.5% gold — the minimum that can legally be called "gold"
Why is gold mixed with other metals?
Pure gold (24K) is a very soft, malleable metal. For jewellery, that softness is a problem: a ring made of pure gold would bend out of shape easily. That is why gold is alloyed with other metals (silver, copper, palladium, zinc) that make it harder and more durable.
These alloying metals also determine the colour: more copper produces rose gold, while more silver and palladium produce white gold.
If you are selling: how value is calculated
When you bring a gold item to a dealer, the first step is determining its caratage through XRF analysis. The value is then calculated as:
Weight × purity × gold price per gram
For example, a 20g bracelet in 18K gold (75% purity), with gold trading at €85/g: 20g × 0.75 × €85 = €1,275 of intrinsic gold value
If you are investing: 24K only
For investment gold, Italian law (Law 7/2000) requires a minimum purity of 995/1000 to qualify for the VAT exemption. In practice, investment bars are always 24K with a purity of 999.9/1000 — the so-called "four nines".
This standard is recognised internationally and guarantees maximum quality and global liquidity.