LemonTrades
TL;DR
- Start with the stamp: 10K, 14K, 18K or 24K (or 417, 585, 750, 999). GP, GEP, HGE, RGP or GF mean plated or filled, not solid gold.
- Home tests (magnet, density, ceramic streak) can rule fakes out but can’t prove a piece is real.
- For anything valuable, an XRF scan at a jeweler or dealer is fast, accurate and doesn’t damage the piece.
- LemonTrades follows the gold price for you and tells you what moved it, and why, within seconds.
Whether it’s an inherited ring or a bar bought online, here’s how to check it, from the quickest look to a test you can trust.
1. Look for the stamp
| Stamp | Gold content |
|---|---|
| 24K or 999 | 99.9% gold |
| 22K or 916 | 91.7% |
| 18K or 750 | 75% |
| 14K or 585 | 58.5% |
| 10K or 417 | 41.7%, the least that can be sold as gold in the US |
| GP, GEP, HGE, RGP | Gold-plated: a very thin layer over another metal |
| GF or 1/20 12K GF | Gold-filled: a thicker layer, but still mostly base metal |
Stamps can be faked, so a stamp is a start, not proof. US rules for how gold may be marked are in the FTC’s jewelry guides.
2. The magnet test
Gold isn’t magnetic. If a piece sticks to a strong magnet, it isn’t solid gold. Many fakes don’t stick either, though. Full details: is gold magnetic?
3. Look for wear
Check edges, clasps and the inside of rings with a magnifier. Plated pieces often show a different color where the gold has worn through.
4. The density test
Weigh the piece in grams, then measure how much water it displaces in a measuring cylinder, in milliliters. Divide weight by volume. Pure gold is 19.3; 18K is roughly 15 to 16, and 14K roughly 13 to 14.5. Brass is about 8.5. It works best on coins and bars, and a kitchen setup isn’t precise enough for small rings.
5. The ceramic streak test
Rub the piece on the back of an unglazed ceramic tile. Real gold leaves a gold streak; a black streak means a fake. It scratches the piece, so don’t use it on anything you care about.
6. The acid test
Jewelers file a tiny scratch and apply acids of different strengths: gold resists acid that dissolves base metals, and the strength that finally affects it tells the karat. Kits are sold online, but the acid is dangerous; a jeweler will usually do it for free or a small fee.
7. The XRF test: the most reliable
An X-ray fluorescence (XRF) scanner reads the metals in a piece in seconds without marking it. Most gold dealers and many jewelers have one. It reads the surface, so for bars bought from unknown sellers, dealers also use ultrasound or electrical conductivity checks to catch tungsten cores.
Fake gold bars and coins
The best fakes are gold-plated tungsten, which weighs almost exactly what gold does. Protect yourself by buying from known dealers or mints, checking a bar’s weight and dimensions against the maker’s specs, and preferring bars in sealed packaging with an assay card. See how much a gold bar weighs.
What real gold is worth today
Sources
- FTC: Guides for the jewelry and precious metals industries (16 CFR 23)
- LBMA: Good Delivery
- Royal Society of Chemistry: Gold
Education, not financial advice. See our disclaimer.
