Can I use this on beads in a bracelet?

Only the bubble check and the temperature check. Beads are usually too small and too opaque for the doubling test.

Does a cold feel prove it is quartz?

No. It reliably rules out plastic, but it is weak against glass. Use it last of the five, not first.

What if I find no bubble at all?

Nothing is proved. Well-made glass can be bubble-free. A negative result moves you to the next check, it does not end the examination.

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Glass, and the five-second check

Diploma in Crystal Identification, Gemmological Institute, China University of Geosciences
Published 27 August 2026 · Revised 27 August 2026 · Six minutes

Glass is the oldest imitation of quartz and still the most common one, for a reason that has nothing to do with craft: it costs almost nothing.

A strand of ordinary natural quartz costs a workshop several hundred New Taiwan dollars at wholesale. The glass version costs tens. Everything downstream of that gap — the vocabulary used in the shop, the lighting above the tray, the reluctance to hand you a loupe — follows from it.

Why the bubble is round

Molten glass traps air, and surface tension pulls that air into the lowest-energy shape available inside a liquid: a sphere. Quartz never passes through a liquid state on its way to being quartz. Its inclusions are shaped by a crystal growing around them over a very long time — angular, feathered, irregular, and almost never fully closed.

So the question at the counter is not "is there a bubble". It is "what shape is it".

Plate I, fig. 1 — drawn, not photographed

The five checks, in order

Look into the stone against a directed light for inclusions, and note their shape.
Look for a perfectly round bubble. One is enough.
Look for flow lines — curved striae left by glass while it was still moving.
Place the stone over printed text. Quartz is doubly refractive; the letters underneath double slightly. Glass is not; they stay single.
Touch it to the inside of your wrist. Quartz draws heat away faster than glass and much faster than plastic.

Where this fails

The doubling test needs thickness and translucency. On a small opaque bead you will see nothing at all — and that absence is not evidence. Say so out loud when you use it.

This is the part most guides leave out, and it is the part worth reading. A method whose edges you cannot see is a method you will eventually misuse.

Questions people ask

Can I use this on a bracelet bead?: Only the bubble and the coldness checks. Beads are usually too small and too opaque for the doubling test.
Does a cold feel prove it is quartz?: No. It rules out plastic reliably and glass only weakly. Use it as the last of the five, not the first.
What if I find no bubble at all?: Nothing is proved. Well-made glass can be bubble-free. A negative result moves you to the next check, it does not end the examination.