Pure gold is soft. A wedding ring made of pure gold scratches and bends with daily wear, so jewellers mix it with other metals (silver, copper, palladium) to give it hardness and colour. Carats tell you how much of that mix is gold. That is all they do.
In this article
What a carat is
The carat divides the piece into 24 parts. 24-carat gold means all 24 parts are gold. 18-carat gold means 18 parts are gold and the other 6 are other metals. To get the percentage, divide the carats by 24: 18 divided by 24 is 0.75, in other words 75% gold.
Be careful, because the word has a second use. With gemstones a carat measures weight, not purity. A one-carat diamond and an 18-carat ring are talking about different things.
Carats and fineness: the table
The other way of saying the same thing is fineness in parts per thousand, which is what Spanish regulations use. The fineness of a piece is the proportion of pure metal it contains, written as a three-digit number. A piece marked 750 holds 750 grams of gold in every kilo of alloy.
| Carats | Fineness | Gold in the piece | Where you see it |
|---|---|---|---|
| 24 | 999 | Practically all of it | Modern investment bars and coins |
| 22 | 916 | 91.6% | Coins such as the Krugerrand, jewellery from other countries |
| 18 | 750 | 75% | Everyday jewellery in Spain |
| 14 | 585 | 58.5% | Cheaper, harder jewellery |
| 9 | 375 | 37.5% | Pieces bought outside Spain |
One detail about 14 carats: the exact division gives 583 parts per thousand, but the mark actually used is 585.
What Spanish rules say
In Spain, gold articles have two official standards: 750 parts per thousand, known as first standard, and 585, the second (article 8 of the Regulation on articles made of precious metals). No downward tolerance is allowed. If a piece falls short of 750 but reaches 585, it is hallmarked as second standard. And if it exceeds the official standard, as a bar does, the assay laboratory can certify the exact proportion.
That is why 375 is not a Spanish mark. If you find it on a piece of jewellery, it most likely came from another country. It still contains gold, 37.5%, and that gold is what you get paid for.
How to read the hallmark
The hallmark is the mark punched into the piece. On jewellery made for sale in Spain you should find two:
- The maker's mark. It identifies the manufacturer or importer, who answers for the piece meeting the rules.
- The guarantee mark. It is applied by an official or authorised laboratory after testing the alloy, and it carries the fineness: 750 or 585.
Look for them with a magnifying glass inside the ring, on the clasp of the chain or on the back of the watch. Gold pieces weighing under three grams are exempt from carrying the stamped mark, so a small pair of earrings may show nothing and still be genuine. In those cases, and whenever the stamp is worn or looks wrong, the only way to know is to have the piece tested.
A stamped number proves nothing on its own. An "18K" with no guarantee mark may or may not be true, and plated pieces carry a layer of gold over another metal. We explain how the metal is checked in certification of physical gold.
"What is bought and sold is the fine gold: the grams of the piece multiplied by its fineness. Everything else is workmanship."
Jewellery gold and investment gold
They are two different products even though the metal is the same.
- Investment gold has a legal definition: bars with a fineness of 995 or above, and coins of 900 or above that meet certain conditions (article 140 of the Spanish VAT Act). It is exempt from VAT. We cover it in investment gold and VAT.
- Jewellery holds less gold, pays VAT, and its price includes design, labour and the shop's margin. When you sell it, almost none of that is recovered: you are paid for the metal.
That is why a piece of jewellery is not an efficient way to hold gold, however beautiful it is, and why a bar is no use for wearing. Each has its job.
Why it matters when you buy or sell
Because the sums are done on the fine gold. A 10-gram chain marked 750 contains 7.5 grams of gold. The same chain marked 585 contains 5.85 grams. They weigh the same on the scales and are worth very different amounts.
- If you sell, ask to be told the weight, the fineness they have tested and the price per gram of fine gold. With those three figures you can compare against the day's quote on our gold and silver price today page. If you bring pieces of different fineness, have them weighed separately.
- If you buy jewellery, the hallmark tells you what you are paying for in metal. The rest of the price is work and brand, which have their value too, but it helps to know how much is which.
- If you buy to hold, look for investment gold and compare by gram of fine gold with everything included.
The step-by-step sum is in how to calculate the price of a gram of gold, and if selling is what you have in mind, see selling gold in Valencia at a fair price.
Frequently asked questions
How much gold is there in an 18-carat piece?
75%. That is 750 parts per thousand: of every 10 grams of the piece, 7.5 are gold and the rest are other metals.
What does the number 750 stamped on jewellery mean?
It is the fineness of the piece in parts per thousand. 750 equals 18 carats and is the first official gold standard in Spain. 585 equals 14 carats and is the second.
Is 24-carat gold better than 18-carat?
It is purer, not better for everything. For holding value, gold of the highest purity is what you want. For jewellery worn every day, 18-carat lasts far better.
Can a piece with no hallmark be gold?
Yes. Pieces under three grams are exempt from carrying the stamped mark, and on old ones the stamp may have worn away. It has to be tested to know.