Gold jewelry ranges from solid 22K to a micro-thin layer of plating over brass, and from a distance they can look identical. The good news is that a careful look and a couple of harmless tests will sort most pieces. The less good news is that no home test can tell you exact purity, and none can be done from a photo. This guide covers what you can check yourself and what a jeweler will do to confirm it.
Start with the stamp
Most solid gold made in the last century carries a purity mark, usually on the inside of a ring band, on a clasp, or on a small tag near the clasp. Use a magnifier and good light.
| Karat mark | Number mark | Gold content |
|---|---|---|
| 9K | 375 | 37.5% |
| 10K | 417 | 41.7% |
| 14K | 585 | 58.5% |
| 18K | 750 | 75% |
| 22K | 916 | 91.6% |
| 24K | 999 | 99.9% |
The number marks are parts per thousand, used widely in Europe and Asia. Some American pieces add a P, as in 14KP, meaning "plumb": the gold content is at least the stated karat, not rounded up. See the hallmarks guide for the full list, including maker's marks and assay marks.
Watch for letters next to the karat mark, because they change the meaning completely:
- GP, GEP, HGE, RGP mean plated or rolled-gold plate, not solid gold.
- GF or something like 1/20 12K GF means gold-filled.
- 18K GP is plated, even though "18K" is right there in the stamp.
A stamp is a strong clue, not proof. Purity marks are easy to strike on any metal, and counterfeit pieces often carry convincing ones. An unmarked piece is not automatically fake either: older, handmade, resized or foreign pieces are often unmarked or the mark has worn away.
Know the four kinds of "gold" jewelry
Solid gold is a gold alloy all the way through. 14K, for example, is 58.5% gold mixed with other metals such as silver, copper or zinc for strength and color.
Gold-filled has a thick layer of gold alloy mechanically bonded to a base metal core, usually brass. In the US, items marked gold-filled must have a gold layer that is at least 1/20 of the item's total weight, so "1/20 12K GF" means a 12K layer making up one twentieth of the weight. Gold-filled wears well for years, but it is not solid gold and has a fraction of the metal value.
Gold vermeil (pronounced "ver-may") in the US means sterling silver with a gold layer of at least 10K and a set minimum thickness. It is more durable than ordinary plating, but the core is silver.
Gold-plated jewelry has a very thin layer of gold applied by electroplating over base metal. "Heavy gold electroplate" (HGE) is thicker but still a surface layer. Plating wears through with use, sometimes within months on rings and bracelets.
Look at the wear
Plating and gold-filled layers wear first where the piece rubs against skin or other surfaces. Check:
- The underside of a ring band and the edges of the shank
- Clasps, jump rings and links that move against each other
- Raised details and corners on pendants and charms
Solid gold looks the same color at worn spots as everywhere else. Plated pieces often show a different color underneath: coppery brass, gray steel or white silver. Green or black marks on your skin, or green spots on the piece itself, usually mean copper-rich base metal showing through. Some solid low-karat gold can mark skin too, so take this as a hint rather than proof.
The magnet test, and its limits
Gold is not magnetic. Hold a strong magnet (a neodymium magnet works best; a fridge magnet is too weak) next to the piece.
- If the piece jumps to the magnet, it is not solid gold, or it contains a significant iron or steel part.
- If nothing happens, that tells you very little. Brass, copper, aluminum, tungsten and many other common base metals are not magnetic either.
Note that clasps often contain a small steel spring, so test the body of the piece, not the clasp.
The ceramic streak test
Some guides suggest dragging the piece across an unglazed ceramic tile (the bottom ring of a mug or plate). Real gold leaves a gold-colored streak; many base metals leave a dark gray or black one.
This test does remove a little metal and can scratch a finished surface, so skip it on anything you value. It also cannot tell 10K from 18K, and on a plated piece you will just be testing the plating. A jeweler's acid test is a more controlled version of the same idea.
The density test
Gold is very dense, so a solid gold piece feels heavy for its size. You can measure density at home with a scale that reads to at least 0.01 g:
- Weigh the piece dry.
- Hang it by a thin thread so it is fully underwater in a cup on the scale, without touching the sides or bottom. The increase in reading is the weight of the water it pushes aside.
- Density = dry weight ÷ that increase.
Pure gold is about 19.3 g/cm³, and karat alloys are lower: 18K is typically somewhere around 15 to 16, and 14K roughly 13 to 14.5, depending on the alloy and color. Brass and copper are far lower, under 9.
Limits: the method only works on pieces without stones, hollow sections or glued parts, and small items give imprecise results. Tungsten has almost the same density as gold, so tungsten-core counterfeits can pass. Use it to rule things out, not to confirm.
What a jeweler will do
If a piece matters, take it to a jeweler or precious-metal buyer. Common professional methods:
- Acid testing. The jeweler rubs the piece on a black touchstone to leave a streak, then applies acids of known strength. Gold of a given karat or higher survives the matching acid, while base metal and lower karats dissolve. It is quick and inexpensive. A jeweler may file a tiny notch first to get below any plating.
- XRF (X-ray fluorescence) analysis. A non-destructive scan that reads the metal composition at the surface in seconds. It is very accurate for solid pieces, but because it reads the surface, a thick plating layer can mislead it, which experienced buyers know to check for.
- Electronic gold testers. Handheld devices that estimate karat from conductivity or electrochemical response.
- Fire assay. The most accurate method, used by refiners. It destroys the sample, so it is used for bullion and scrap rather than jewelry you want to keep.
What a photo can and cannot tell you
A clear photo can show the style of a piece, the type of chain or setting, visible wear, and sometimes a readable stamp. That is enough to suggest whether a piece is likely fine jewelry or costume, and roughly when and where it was made. AI Jewelry uses those visual details, together with any marks it can see, to describe the metals and explain its price range.
A photo cannot measure purity, detect plating thickness or weigh the piece, and those three things drive gold value. Treat any app result as a starting point, then confirm with a physical test.
Tip: before visiting a buyer, weigh the piece yourself in grams and note the stamp. It makes it much easier to judge whether an offer is fair. Our guide to how much your jewelry is worth shows how to work out melt value.
A quick checklist
- Find and read the stamp, including any letters after the karat.
- Check worn edges for a different color underneath.
- Try a strong magnet on the body of the piece.
- For stone-free pieces, try a density measurement.
- Confirm anything valuable with an acid or XRF test at a jeweler.
If the gold is set with stones, see how to tell if a diamond is real as well.