5 At-Home Tests to Spot Fake Gold Before You Sell or Buy

Before reselling inherited jewellery, accepting a "vintage" piece from a private seller, or simply verifying a recent purchase, run these five tests. None replaces a professional test — but together they can flag many obvious fakes.

Test 1 — The hallmark check

Solid gold pieces (24K, 22K, 21K, 18K, 14K) usually carry a stamp indicating purity:

Look on the clasp, the inside of a ring band, or the back of a pendant. Use a 10× jeweller's loupe (~$10 on Amazon) for fine detail. Stamps that say "GP" (gold-plated), "GF" (gold-filled), "1/20 12K GF" (12K gold-filled rolled to 1/20 weight), or "RGP" (rolled gold plate) are NOT solid gold — they have a thin gold layer over a base metal core.

Test 2 — The magnet test

Pure gold is NOT magnetic. Hold a strong neodymium magnet (a small one from any DIY store) close to the piece:

• No attraction at all → consistent with gold (but doesn't prove gold; brass, copper, lead also non-magnetic)
• Strong pull → contains a magnetic metal such as iron or steel → not solid gold (a clasp's small steel spring can also attract, so test the body of the piece)

This test catches steel-core "gold" pieces. It doesn't catch gold-coloured brass or copper.

Test 3 — The density test

Gold is heavy. Density: 19.3 g/cm³ for pure gold; about 17 g/cm³ for 21K; about 15.5 g/cm³ for 18K; about 13–14 g/cm³ for 14K (the exact figure depends on the alloy). Most fake metals (brass, copper, zinc alloys) sit at 7.5–8.9 g/cm³ — roughly half the density.

Method:

1. Weigh the piece on a scale that reads to 0.01 g if possible (mass in grams = M)
2. Put a cup of water on the scale and press tare/zero
3. Hang the piece on a thin thread so it is fully under water without touching the cup; the new reading in grams equals its volume in cm³ (V)
4. Density = M / V

A 21K piece should land close to 17 g/cm³ (readings on small pieces are rough). A brass fake will land near 8 g/cm³. Half the density = fake. A normal reading does not prove gold: tungsten is almost as dense as gold and has been used in counterfeits.

Test 4 — The ceramic scratch test

Buy a small unglazed ceramic tile (a "streak plate" — $5 at lapidary supply or hardware). Drag the gold piece firmly across the tile:

• Gold streak (yellowish) → consistent with gold
• Black streak → pyrite ("fool's gold") or gold-plated brass
• No streak at all → too hard; could be steel, ceramic, or other non-gold metal

This is a destructive test on the surface of the jewellery (very minor scratch) — only use on pieces you intend to sell or are confident are fake.

Test 5 — The nitric acid test (advanced)

The most informative home test, but it requires care. Gold-testing kits include:

• Testing acids for different karats (nitric acid, plus nitric–hydrochloric mixes for higher karats)
• Pipette dropper
• A black touchstone

Method:

1. Lightly scratch the piece on the test stone, leaving a small gold streak
2. Put one drop of the acid for the karat you want to test on the streak
3. Streak stays unchanged → the metal is at least the karat of the acid you used (an 18K acid leaves 18K and higher untouched but dissolves lower-karat gold)
4. Streak turns green → base metal (brass, copper alloys)
5. Streak fades or dissolves → lower karat than the acid, or not gold at all. Gold does not dissolve in nitric acid, which dissolves silver and base metals — so a plated piece fails once the streak reaches the base metal under the thin gold layer

Safety: wear gloves and eye protection. Work outside or in a well-ventilated area. Neutralise spilled acid with baking soda before disposal.

When to walk to a professional

If two or more of the above tests fail OR if the piece is high-value (>$500 USD), get a professional XRF assay. Many gold dealers and assay offices offer XRF testing, which is quick and does not damage the piece.

What you can do today

1. Loupe + hallmark check — 30 seconds, costs nothing
2. Magnet test — 10 seconds with a strong neodymium magnet (not a weak fridge magnet)
3. Weigh on a kitchen scale, cross-check against our calculator for expected market value at the stated weight and karat

If the math doesn't match — if a "50g 21K" piece weighs 35g, or the seller wants 60% of spot value for a "guaranteed 24K" coin — walk away. Genuine gold is rarely offered far below its spot value.

Bookmark our 24K page for the daily reference, and check it before any private-market transaction.