How to tell if jewelry is real gold, starting with the stamp

Step one: find the stamp

Look inside the band of a ring, on the clasp of a chain or the small tag beside it, on the post or back of an earring, on the inside of a bangle, and on the back of a pendant or brooch. Stamps are tiny, so use a loupe, a magnifying glass or the zoom on a phone camera, in good light.

What a karat stamp means

Under the Federal Trade Commission’s jewelry guides (16 CFR Part 23), the word “gold” on its own means fine, 24 karat gold, and gold alloy should carry a correct karat designation before the word, as in “14 Kt. gold”. The karat tells you the share of pure gold: karat divided by 24.

Karat stamps and their pure gold share

Stamp	Pure gold share
10K, 10KT, 10 Kt.	41.7%
14K, 14KT, 14 Kt.	58.3%
18K, 18KT, 18 Kt.	75%
22K, 22KT, 22 Kt.	91.7%

A karat stamp is a strong sign, though not a guarantee: a stamp can be worn, misleading, or applied to a piece it does not describe. That is why a test can matter.

What a plated stamp means

Some stamps tell you a piece is not solid gold. The FTC guides reserve terms such as “Gold Plate”, “Gold Plated”, “Gold Overlay” and “Rolled Gold Plate” for a layer of gold alloy of at least 10 karat over another metal, with the karat of the plating stated before the term. A stamp like “1/40 12 Kt. R.G.P.” means rolled gold plate: the 12 Kt. describes the thin layer, not the piece. Look for a plated term or its abbreviation, such as “R.G.P.”, next to a karat.

Plated items are not solid gold. They have a thin layer of gold and very little gold value.

What sterling means, in case it is silver

If the stamp reads “sterling”, “ster.” or “925”, the piece is silver, not gold: under the FTC guides those words mean at least 92.5% silver. A gold-colored piece stamped 925 is silver with a gold-colored surface, and it is valued as silver.

Simple checks at home

These are general tips, not tests that prove anything. They can rule a piece out; they cannot rule it in.

• Look at wear. Rub the edges, clasps and high points. If a different color metal shows through where the piece rubs, it is likely plated.
• Try a magnet. Gold is not magnetic. If a strong magnet pulls the piece, the metal under it is not gold, though a clasp spring may be steel on a real gold chain, and many non-gold metals are not magnetic either.
• Check the weight in your hand. Gold is dense, so a solid piece feels heavy for its size. Hollow gold chains are an exception: they are real gold but light.
• Look at your skin. A green or dark mark on the skin after wear points to other metals, though alloys in low-karat gold can mark skin too.

Avoid scratching, filing or using acid on a piece yourself. Home acid kits can damage jewelry and are easy to misread.

When to let a buyer test it

A buyer can test metal by methods that do not depend on the stamp. For a piece with a worn or doubtful mark, ask whether and how it will be tested before an offer is made. In New York City, a buyer must also weigh precious metal on a State-approved scale and tell you the troy weight, so a test and a weight together tell you what you have.

Gold may test slightly under its mark within legal limits. The National Stamping Act, cited in the FTC guides, allows up to three parts per thousand under for gold with no solder and up to seven with solder.

Once you know it is gold

Weigh it in grams, divide by 31.10348 to get troy ounces (NIST SP 811), and multiply by the gold share and the day’s spot price to get the melt value. The guide to selling gold jewelry explains how buyers price gold and how to compare offers, and 10K versus 14K gold shows what the karat difference means in pure gold.

Questions people ask