How to read gold purity marks

Karat and millesimal marks

Most jewelry gold is an alloy. Other metals are added so a ring or chain can hold its shape. Purity is the gold share of that mix.

Common karat values

Karat (often stamped K or KT) is a 24-part scale. 24 karat is fine gold. 18 karat is 18 parts gold in 24, or 75 percent. 14 karat is 14 parts in 24, often stamped 14K. 10 karat is 10 parts in 24. Lower karat gold is still gold. It is a different mix.

Millesimal stamps

A millesimal mark states parts per thousand. 999 or 999.9 is fine gold. 750 matches 18 karat. 585 or 583 matches 14 karat. 417 matches 10 karat. Some older European pieces use only the number. Some U.S. pieces use only the karat stamp. Some use both.

Karat is not carat

Karat describes gold purity. Carat describes the weight of a gemstone. A diamond listed as one carat is a weight, not a gold stamp. The two words sound alike. They answer different questions.

What hallmarks can and cannot tell you

A stamp is a starting point. It can be worn, moved from another piece, or missing. Plated items can carry a stamp that describes the surface, not the core. That is why a mark is read with a test, not instead of a test. Maker marks, when present, are a separate fact from purity.

What we look for

At the counter we read karat or millesimal stamps, then weigh the piece where you can see the scale. Stones and mixed metals are noted separately from the gold. A missing stamp does not stop the visit. We still test and explain what we found before any offer.