Sometimes, the two types of plastic and glass beads cannot be distinguishable from each other. Thus, a few tricks are needed to tell the difference between plastic beads and glass crystal beads as follow:
1. Heat up the beads using fire (lighter fire for example). Plastic beads melt. Crystal glass will not melt.
2. Pick up the bead in your bare hand. Glass beads initially feel cool to the touch, because they are much denser than acrylic beads, which are most commonly used to imitate the glass beads. On the other side, the glass beads warm up pretty quickly in the hand, while it takes longer for the acrylic beads to change temperature.
3. Measure the weight of the beads. Generally, the acrylic beads are much lighter than glass beads.
4. If you have spare beads, you can also tell the difference by lightly tapping them with a hammer. Place the bead on a hard surface and tap it with the hammer. A glass bead will crack quite easily, while the hammer will bounce off a plastic bead under a light blow.