Gold Identifier
The Three Things You Might Be Holding
| Solid gold | Gold plated / filled | Brass | |
|---|---|---|---|
| What it is | Gold alloyed with other metals throughout | A gold layer bonded over a base metal core | Copper and zinc alloy: no gold at all |
| Typical marks | 999, 916, 750, 585, 375, 18K, 14K | GP, GEP, HGE, GF, 1/20 12K GF, RGP, vermeil | Usually unmarked, or a brand name only |
| Density | 12.9–19.3 g/cm³, very heavy | Close to the core metal, light | ~8.5 g/cm³, light |
| Tarnish | Does not tarnish | Wears through, revealing base metal | Darkens and develops a dull patina |
| Skin reaction | Rare | Green marks once worn through | Commonly leaves green marks |
| Value | Metal value, substantial | Negligible gold; base-metal value | Scrap brass value only |
1. Read the Stamp First
This resolves most cases in ten seconds. Solid gold carries a purity mark: 999, 916, 875, 750, 585, 417, 375, or a karat mark like 18K or 9ct.
These marks mean it is not solid gold:
- GP / GEP: gold plated or gold electroplated. A layer often under a micron thick.
- HGE / HGP: heavy gold electroplate. Thicker, still trivial in metal terms.
- GF or 1/20 12K GF: gold filled. A bonded layer that is typically 1/20th, or 5%, of the total weight. More gold than plating, but the core is brass.
- RGP: rolled gold plate. Thinner than gold filled.
- Vermeil: gold over sterling silver. The silver has real value; the gold layer does not.
- 925 on a gold-colored piece: sterling silver with gold plating.
Brass jewelry usually carries no purity stamp at all, just a brand name, or nothing. The full decoder is in our hallmark guide.
2. Look at the Wear Points
This is the most reliable visual test, and it costs nothing. Plating wears through where the piece rubs: the underside of a ring shank, the edges of a bangle, the back of a pendant, the high points of a textured surface, the clasp of a chain.
Examine those spots in good light with your phone's macro mode. If you see a duller, whiter, greyer or pinker metal showing through a gold-colored surface, you have plating over base metal. Solid gold has the same color all the way through: it wears thinner but never changes color.
Brass, by contrast, doesn't wear through because it is the same alloy throughout, but it does darken over time, developing a dull brownish patina in crevices while the rubbed areas stay bright. Gold never does this.
3. Weigh It in Your Hand
Gold is exceptionally dense. Brass is not.
| Metal | Density (g/cm³) |
|---|---|
| Pure gold (24K) | 19.3 |
| 22K gold | 17.7–17.8 |
| 18K gold | 15.2–15.9 |
| 14K gold | 12.9–14.6 |
| Brass | 8.4–8.7 |
| Steel | 7.8 |
| Silver | 10.5 |
A solid gold item feels roughly twice as heavy as a brass item of the same size. Once you have handled real gold a few times, the difference becomes obvious by feel alone: pick up a chunky "gold" ring that feels like plastic and you already have your answer.
4. The Magnet Test
Neither gold nor brass is magnetic, so a magnet will not separate them. What it will do is catch cheap plated jewelry with a steel or iron core, which is very common. Use a strong neodymium magnet, not a fridge magnet. Any attraction at all means base metal inside.
5. Skin and Smell
- Green marks on your skin come from copper reacting with sweat. Brass is roughly two-thirds copper, so it does this readily. Plated pieces do it once the plating wears through. Solid high-karat gold rarely does.
- The smell. Rub the piece vigorously between your fingers and smell them. Brass and copper leave a distinct sharp, metallic, slightly sour odor. Gold is odorless.
6. The Ceramic Streak Test
Drag the item firmly across unglazed ceramic: the unfinished underside of a bathroom tile. Solid gold leaves a gold-colored streak. Brass and plated base metal leave a black or dark grey streak. It is cheap and decisive, but it scratches the item, so pick a hidden spot and skip it entirely on antiques.
7. The Acid Test
A $20 testing kit settles it definitively for jewelry. Rub the piece on the supplied stone, apply the acid for the karat you suspect, and read the result. Brass reacts immediately and vigorously. Plating passes on the surface but fails once you file a notch through it, which is exactly why professional buyers always file first.
Is Gold-Plated Jewelry Worth Anything?
Honestly, very little as metal. A typical plated piece carries a fraction of a gram of gold spread over the surface, and recovering it costs more than it is worth. Refiners will generally not buy plated items at all.
Gold-filled is different in degree: at roughly 5% of total weight in gold, a heavy gold-filled item has some recoverable value, and specialist buyers do purchase it in bulk. Vermeil carries the value of its sterling silver core.
Where plated jewelry does hold value is as jewelry: a well-designed or collectible piece is worth what someone will pay for it, quite apart from its metal.
A Fast Decision Sequence
- Look for a stamp. A purity number suggests solid; GP, GF, HGE or RGP settles it as plated.
- Inspect the wear points under macro. Different metal showing through means plated.
- Weigh it in your hand. Suspiciously light for its size means brass or a hollow plated core.
- Try a strong magnet. Any pull means a ferrous core.
- Rub and smell. A sharp metallic odor means copper alloy.
- If it still matters, test it. Acid kit or a free XRF scan at a jeweler. See all eight methods.
Spot the Difference From a Photo
Gold Identifier flags plating wear, reads stamps like GP and GF, and tells you what the piece most likely is. Free on iPhone and Android.