Stones that look alike: how to tell them apart

As polished beads a few millimetres across, stones lose much of what makes them recognisable: crystal shape, fracture, size. What remains is colour, lustre and pattern, and these clues look alike from one stone to another. Add treatments (dyeing, heating) that bring appearances even closer, and trade names that are sometimes misleading.

First, the light test: hold the bead in front of a lamp or window. A translucent stone such as agate, carnelian or moonstone lets light through; jasper or howlite does not.

Then the loupe: a jeweller's loupe reveals aventurine's glitter, the pyrite specks in lapis lazuli, the bubbles in glass. Finally, your hand: stones feel cool and warm up slowly, whereas plastic or resin feels warm straight away.

You'll sometimes read that scratching a stone tests its hardness. True in a lab, but on jewellery it leaves a permanent mark. Likewise, flame or acetone tests can damage a stabilised or dyed stone. For a valuable stone, a gemmologist is the only real certainty.

Ask the seller: where does the stone come from, is it dyed, heated, stabilised? A clear answer is a good sign. Our guide “Natural, dyed or heated stones” covers the most common treatments and what French law says.