The gold guide

What K18 means, how to read a stamp, and how to keep a piece looking right. The things worth knowing before you buy.

Illustration of a K18 yellow gold chain clasp, with a K18 stamp and a hallmark struck into the clasp plate. — PlatinumPlatinum is marked the same way, e.g. “Pt900”.

Illustration of the same style of clasp in platinum, stamped Pt900. — PlatinumPlatinum is marked the same way, e.g. “Pt900”.

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What K18 means

K18 is 75% gold. The remaining 25% is alloy — usually silver and copper — and it is what sets the hardness and the colour. K24 is pure gold and too soft for jewelry you actually wear. K18 is the fine-jewelry standard in Japan. In Europe the same standard is marked 750 or Au750, and in English-speaking markets 18K: K18, 750, 18K and Au750 all denote the same 75% purity. We show the stamp as it appears on the piece.

Gold content: 75%
Same standard: 750 / 18K / Au750
Daily wear: Suitable

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How to read the stamp

Gold carries a K18 or 750 stamp plus a maker's mark. Platinum is marked PT900 or PT950. The stamp sits somewhere discreet: look at the flat tab on a necklace clasp, the inside of a ring band, or the post of an earring.

Gold: K18 / 750
Platinum: PT900 / PT950
Where to look: Clasp tab, ring inside, earring post

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Care

Warm water, a mild soap and a soft cloth. Store pieces separately so they do not rub against each other, and keep them away from hot springs and chlorine, which discolour the metal. Pearls need wiping after every wear and restringing every few years.

Cleaning: Warm water, mild soap
Avoid: Hot springs, chlorine
Pearls: Wipe after wear, restring every few years

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