Real gold doesn’t tarnish, isn’t magnetic, and leaves a specific golden streak on unglazed ceramic. You can check most of these things at home in a few minutes with items you probably already own. No single test is 100% conclusive on its own, but combining two or three of them gives you a reliable answer before you ever visit a jeweler.
Check for Hallmarks and Stamps
The fastest first step is looking for a stamp. Genuine gold jewelry is almost always marked with its karat value, either as a familiar abbreviation or a three-digit number representing the percentage of pure gold in the piece. The most common stamps you’ll find:
- 417 or 10K: 41.7% pure gold
- 585 or 14K: 58.5% pure gold
- 750 or 18K: 75% pure gold
- 917 or 22K: 91.7% pure gold
- 999 or 24K: 99.9% pure gold
Use a magnifying glass and check the inside of rings, the clasp area of necklaces, or the post of earrings. If you see “GP” (gold plated), “GF” (gold filled), or “HGE” (heavy gold electroplate), the item has a thin gold coating over a cheaper metal. A missing stamp doesn’t automatically mean the piece is fake, especially on older or handmade items, but it’s a reason to keep testing.
The Magnet Test
Pure gold is not magnetic. It’s actually very slightly repelled by magnets, a property physicists call diamagnetic. If you hold a reasonably strong magnet (a fridge magnet is too weak, but a neodymium magnet from a hardware store works well) near your item and it snaps toward the magnet, it contains iron or another highly magnetic metal and is not solid gold.
The catch: passing the magnet test doesn’t prove something is gold. Plenty of non-magnetic metals look like gold. Aluminum, copper, and brass won’t react to a magnet either. Think of the magnet test as a quick way to rule out obvious fakes rather than confirm the real thing.
The Ceramic Streak Test
This one is simple and surprisingly informative. Find an unglazed ceramic tile or the unglazed bottom of a ceramic plate. Drag your gold item across it firmly enough to leave a mark, but not so hard you gouge the piece.
Real gold leaves a golden-yellow streak. Pyrite (fool’s gold) leaves a greenish-black to brownish-black streak, and brass typically leaves a darker mark as well. If the streak is anything other than gold-colored, the item isn’t solid gold. Keep in mind this will create a small scratch on the item, so use it on an inconspicuous spot if the piece has sentimental or resale value.
The Vinegar Test
Place your item in a small bowl and add a few drops of plain white vinegar. Gold is chemically non-reactive, so pure gold won’t change color at all. Fake gold or base metals coated in gold may turn black or green within a few minutes as the acid in the vinegar reacts with the underlying metal. Rinse the item with water afterward. This is a gentle, low-risk test, though it’s better at catching obvious fakes than distinguishing between different karat levels.
The Density (Water Displacement) Test
Gold is extremely dense. Pure 24K gold has a specific gravity of 19.3 grams per cubic centimeter, which means it’s about 19 times heavier than the same volume of water. Most metals used to fake gold are significantly lighter.
To test this at home, you need a kitchen scale accurate to at least 0.1 grams and a container of water. First, weigh the item in grams. Then fill a container with water, note the water level (or use a graduated cylinder for precision), and drop the item in. The rise in water level gives you the volume in milliliters, which equals cubic centimeters. Divide the weight by the volume. If the result is close to 19.3, the item is likely pure gold. Lower karat gold will have a lower density because of the other metals mixed in, typically around 11 to 15 depending on the alloy, but it should still feel noticeably heavy for its size. If the number comes back around 5 to 8, you’re probably looking at brass or a plated base metal.
This test works best for solid items like coins or bars. Hollow jewelry, stones, or items with clasps and mechanisms will throw off the measurement.
Acid Testing Kits
Acid test kits, available online and at jewelry supply stores, use chemical solutions to react with the metal’s surface. You scratch the item on a testing stone to leave a small deposit, then apply a drop of the appropriate acid solution. The color of the reaction tells you what you’re dealing with.
A bright green reaction indicates gold plating over copper or brass. A pinkish cream color suggests gold plating over silver. For items that are genuinely gold, a 10-karat piece will show a slight reaction to the first testing solution, while anything above 10 karats shows little to no reaction. Stronger acid solutions in the kit help you narrow down higher karat values: 14K to 18K gold reacts slightly to a medium-strength solution, and only gold above 18K reacts to the strongest solution (a mixture called aqua regia).
Acid testing is more precise than home methods like vinegar, but it does leave a tiny scratch where you scrape the sample. It’s the method many pawn shops and independent jewelers use for quick assessments.
How to Spot Gold Plating Wearing Off
If an item was gold-plated rather than solid gold, time and friction will eventually reveal the truth. Look carefully at edges, corners, clasps, and any area that gets regular contact with skin or clothing. Gold plating wears through at these high-friction points first, exposing a different-colored metal underneath. A silvery or reddish tint peeking through at the edges is a clear sign of plating over nickel, steel, or copper.
Plated items also tend to cause skin discoloration. If a ring consistently leaves a green or black mark on your finger, the gold layer is thin enough that your sweat is reacting with the base metal beneath it.
Gold vs. Fool’s Gold (Pyrite)
If you’re examining a rock or mineral specimen rather than jewelry, the question is usually whether you’re looking at gold or pyrite. They look similar at a glance, but they behave very differently.
The biggest giveaway is hardness. Gold is one of the softest metals, rating about 3 on the Mohs hardness scale. You can scratch it with a pocket knife, and it bends or flattens easily without breaking. Pyrite sits at 6 on the same scale. It scratches copper, resists a knife blade, and shatters like glass if you hit it with a hammer. Try pressing a pin or knife tip into the specimen: if it dents and deforms, that’s consistent with gold. If it resists or chips, it’s pyrite.
Shape is another clue. Pyrite tends to form angular, cube-like crystals with flat, even faces. Gold in nature forms irregular nuggets, flakes, or thin sheets that look like they’ve been squeezed and folded. And the streak test mentioned earlier works perfectly here: gold on unglazed ceramic leaves a yellow streak, while pyrite always leaves a black one.
Professional XRF Testing
When the stakes are high, like buying a significant piece of jewelry or verifying an investment, professional testing removes the guesswork. The gold standard (literally) is X-ray fluorescence, or XRF. A benchtop XRF analyzer directs X-rays at the item, which causes the atoms in the metal to emit their own secondary X-rays at energies unique to each element. The machine reads those emissions and reports exactly which elements are present and in what percentages.
XRF testing is completely nondestructive. Nothing is scratched, dissolved, or damaged. Many jewelers, pawn shops, and precious metal dealers have XRF machines on site, and testing typically takes under a minute. If you’re spending serious money on gold, the small fee for an XRF analysis is worth the certainty.