Karat is a fraction out of 24. 24K is close to pure, 22K is 91.7% gold, 18K is 75%, 14K is 58.3% and 10K is 41.7%. A stamp is a claim, not a guarantee: a 2023 Gemological Institute of America study found that 31% of unverified 14K listings online failed acid testing, coming back as lower-karat alloy or gold-filled. Weigh the piece, calculate what that karat should be worth, and get an XRF reading before any purchase large enough to hurt.
What the number on the stamp means
Karat is a fraction of 24 parts. 24K is 99.9% gold, 22K is 91.7%, 18K is 75%, 14K is 58.3% and 10K is 41.7%.
This matters more than most buyers expect. A 14K piece is closer to half gold than to all gold. Two chains of identical weight, one 22K and one 10K, differ by more than a factor of two in metal value.
Higher karat is softer. 24K scratches and bends easily, which is why most wearable jewelry is 18K or below. Lower karat is not a trick; it is a durability decision. It only becomes a problem when the price does not reflect it.
A stamp is a claim, not proof
Genuine gold jewelry almost always carries a hallmark, so a missing mark is a warning. But the reverse does not hold: a stamp is easy to fake, especially on mass-produced or imported items.
The GIA tested unverified 14K listings sold online and found that 31% failed acid testing, returning either a lower-karat alloy or a gold-filled core.
Two specific tricks are worth knowing. On gold-filled pieces, the original marking is sometimes removed and replaced with a fake solid-gold stamp such as 14k or 585. On chains and bracelets, the clasp and end rings are sometimes genuine gold and hallmarked while the length of the chain is base metal.
Checks you can make yourself
Weigh it and do the arithmetic. Multiply the weight by the karat purity and the spot price per gram. If the asking price sits below that metal value, the piece is almost certainly not the karat it claims. Nobody sells gold below melt by accident.
Check the whole item, not one end. Look for a hallmark on the clasp and on the body. A mark in one place only is worth questioning on a chain.
A magnet test rules things out but proves nothing. Gold is not magnetic, so a piece that jumps to a magnet is not solid gold, but plenty of non-gold metals are also non-magnetic.
Look for wear at the edges and high points. Plating wears through at corners and clasps first, showing a different color underneath.
The check that actually settles it
An XRF analyzer reads the exact metal composition without damaging the piece, and it is the only method that gives a definitive karat reading. Many jewelers and gold buyers have one.
Acid testing is cheaper and widely available, but it marks the piece and reads only the surface, so it can be fooled by a thick plating over base metal.
For any purchase large enough that being wrong would hurt, pay for an independent test before you buy, from someone who is not selling you the item. The cost is small against the price of a piece that turns out to be gold-filled.
Buying secondhand or online raises the stakes, because the seller may not know either. A stamp inherited from a previous owner carries no more authority than a stamp applied last week.
Common questions
How much gold is actually in 14K?
58.3%. Karat is a fraction of 24 parts, so 14K is 14/24 gold and the rest is alloy. That is why a 14K piece is worth roughly half what the same weight of 24K would be, and why the karat matters as much as the weight when you calculate value.
Does a 14K stamp mean the gold is real?
No. A hallmark is a claim by whoever made or marked the piece. A 2023 GIA study of unverified 14K listings sold online found 31% failed acid testing, returning lower-karat alloy or a gold-filled core. Stamps can be forged, and on gold-filled items the original marking is sometimes removed and replaced.
How can I tell if gold is plated?
Look for wear at edges, corners and clasps, where plating rubs through first and shows a different color underneath. A magnet test can rule a piece out, since gold is not magnetic, but it cannot confirm anything. Only an XRF reading gives a definitive answer without damaging the item.
Is a hallmark on the clasp enough?
Not on a chain. One known tactic is a genuine hallmarked gold clasp attached to a chain made of base metal. Check for marks on the body of the piece as well as the fittings, and have the whole item tested if the value is significant.