You can read the karat marking on the small hallmark located inside the ring band, on the clasp of the necklace, or on the back of a pendant. The hallmark is either a three-digit number - typically 333, 375, 585 or 750 - or a marking with "K" or "kt" after a number, for example 14K. Both tell you the same thing: how large a proportion of the piece is pure gold. A hallmark of 585 corresponds to 14 karat gold, and that is the purity most of Longvé's jewellery is made in.

Karat describes the gold content on a scale from 1 to 24, where 24 karat is pure gold. Pure gold is too soft for jewellery that is worn daily, so it is alloyed with other metals to make it stronger. The lower the karat number, the more of the other metals there are in the alloy. It is precisely the ratio between gold and the other metals that the three-digit hallmark puts a number on.

How to convert the three-digit hallmark to karat

The three-digit hallmark indicates the gold content in thousandths. The number 585 means that 585 out of 1000 parts are pure gold - that is, 58.5 percent. To find the karat number, you divide the gold proportion against the 24 karat that corresponds to pure gold.

The most common hallmarks and their karat look like this:

So if you see 585 inside a ring, you are holding 14 karat gold. A hallmark of 750 is 18 karat, and 333 is 8 karat. The three-digit system is used widely in Europe, while the marking with K is more often seen on jewellery from the USA, among other places.

Where is the hallmark located, and how do you find it?

On a ring, the hallmark is almost always located on the inside of the ring band. On a necklace, you often find it on a small plate by the clasp or on the clasp itself, and on a pendant typically on the back. Earrings are hallmarked on the post or on the hook, if there is room.

The hallmarks are small, and the digits can be hard to distinguish with the naked eye. A loupe or a good magnifying glass makes it easier to read the numbers correctly, especially on thin pieces of jewellery where space is scarce. If the piece is worn, an old hallmark may be partially rubbed away, and then it may require a goldsmith to determine the purity reliably.

What do the letters next to the number mean?

In addition to the karat or purity hallmark, many pieces of jewellery carry a maker's or manufacturer's mark - a letter or figure mark showing who made or imported the piece. It says nothing about the gold content, but functions as a kind of signature from the producer.

A "K" or "kt" after a number, as in 14K, is instead a direct karat marking and should be read as 14 karat. If you see both a three-digit hallmark and a K hallmark on the same piece, they simply indicate the same thing in two ways.

Does the hallmarking also apply to white gold?

Yes. White gold is gold alloyed with white metals that give the light colour, but the gold content is measured on the same scale as gold. A hallmark of 585 on a white piece therefore means 14 karat white gold - exactly as on a piece in the yellow shade. Purity is about the amount of pure gold, not about the colour. If you want to read more about how the white shade comes about, Longvé has an article on what white gold is. Among Longvé's jewellery, both shades are available in both gold and white gold, both in 14 karat.

What does 925 mean, if it is not gold?

If it says 925 on a piece of jewellery, it is not a gold marking, but the hallmark for sterling silver - 92.5 percent pure silver. It is easy to confuse with a gold hallmark, because it is also a three-digit number, but the system is the same: the number indicates the purity of the precious metal in thousandths. A silver piece can therefore never have a karat hallmark such as 585 or 750. At Longvé, sterling silver is used for signet rings, among other things. You can read more about what 925 means in a ring.

Why do most people choose 14 karat for jewellery worn daily?

A higher karat number means more gold and thus a warmer, more intense colour, but also a softer metal. 24 karat gold scratches and bends easily and is not suited for rings and bracelets that are in constant use. 14 karat gold hits a point where the gold colour is clear, while the alloy is at the same time hard enough to withstand daily wear. That is the reason this particular purity recurs throughout the majority of Longvé's range, from rings to necklaces.