How to tell fake crystals by sound: the tap test, done right

The illustration at the top was made with AI tools.

People bring a stone to our counter in Peckham and tap it on the glass, then look at me. The tap is a real test, and it is the one most videos show, but it is smaller than it looks. This is what the sound actually tells you, and the three checks that settle the question.

What the tap test is listening for

Hold the piece by its edge between finger and thumb, with as little of your hand touching it as you can, and tap it with a fingernail or a coin. A genuine quartz piece gives a clear note that carries for about a second and then fades. Glass, resin and acrylic give a short, dead click with almost no ring.

The reason is structure. Quartz is crystalline: the lattice carries the vibration and hands it back, so you hear a note. Glass is amorphous, so the same tap is damped almost immediately. It is the same difference you hear between tapping a wine glass and tapping a lump of ice.

• Hold the piece by the edge, never flat in the palm — your hand damps the ring.
• Tap with a fingernail or a coin, and tap the same way on every piece you compare.
• Listen for how long the note lasts, not how loud it is.
• Tap a known piece next to the unknown one. A comparison is worth more than a description.

Why the sound test can lie

A small stone cannot ring like a large one. A thick palm stone the size of a fist will thud even when it is solid quartz. A thin slice or a long point will sing. Shape and mass do most of the work, so a dull sound is not proof of a fake, and a bright sound is not proof of a real stone.

• Set stones: a bezel, a glued base or a wire cage damps the ring completely.
• Beads: drilled and strung, so the cord and the neighbouring beads kill the note.
• Thick glass: a chunky glass bead can ring clearly, which is exactly why the test is not enough on its own.
• Clusters and geodes: rough, porous pieces do not ring, whatever they are made of.

If the piece is set, strung or rough, treat the tap as no evidence at all and use the checks below.

Three checks to pair with it

1. Cold and weight. A stone feels cold when you pick it up and stays cold for a minute or more. Glass warms quickly in the hand. Resin and plastic are light for their size and feel warm from the start.

2. Look inside. Glass shows round bubbles and swirl lines, and its colour is perfectly even. Resin fakes usually have a seam from the mould and a uniform glitter that sits flat. Dyed stone shows colour pooled in cracks and around the drill hole. Real quartz has inclusions, phantoms, growth lines and uneven colour, and no bubbles.

3. Hardness. Quartz is 7 on the Mohs scale; glass is about 5.5. A quartz point will scratch a glass bottle; glass will not scratch quartz. Do it on the underside or the base where a mark will not show, never on the face. Steel is around 5 to 5.5, so a steel pin is not a useful test on quartz.

If you want a fourth check, a cheap UV torch helps: many dyes and resins glow under it in a way natural quartz does not.

The fakes you actually meet

• Glass, sold as quartz, obsidian or “opalite”. Bubbles, even colour, warm to the touch.
• Resin with glitter, sold as orgonite or “aura” clusters. Light, warm, seams, no cold.
• Dyed quartz. Real stone, wrong colour: the dye pools in cracks and fades in sunlight.
• Heat-treated and coated amethyst. Real quartz, but the colour is not natural, and the price should say so.
• Reconstituted stone. Crushed stone set in resin. It is partly real, it is not a crystal.

None of that means the seller is dishonest. Most of it is sold in good faith as decorative stone. The job is to know what you are paying for.

Doing it at the counter

We keep a known piece of quartz and a glass bead behind the counter for exactly this. Two taps and a look inside the stone answers most questions in under a minute. If you are buying online, ask the seller for a short video of the piece being tapped, and for a close-up in daylight — that is the honest version of this test.

If you already own a piece and want to know what it is worth rather than whether it is real, photograph it and use the free Value Scanner first. For a piece that matters, the Society Valuation takes it further: we confirm the species, measure it and price it against what similar pieces actually sell for.

Want to read more on specific stones? The amethyst meaning guide, the lapis lazuli price guide, amazonite benefits and smoky quartz meaning all cover what to look for in that stone.

Questions people ask

Does a real crystal always ring when you tap it?

No. A thick palm stone, a small cabochon, or a bead glued into a setting can sound dull even when the stone is genuine. Size, shape and how it is held change the note more than the material does.

Can a fake crystal ring?

Yes. A thick glass bead can give a clear note, and some glass imitations are made to. That is why the tap is one clue among several, not a verdict on its own.

How do I test a crystal bracelet?

Drilled, strung beads are damped by the cord and by each other, so the tap is weak evidence there. Weigh it in the hand, feel whether it stays cold, and look at the colour and inclusions instead.