Rondelle

The dictionary definition of rondelle is a small disk of glass used as an ornament in a stained-glass window or in jewellery making a flat bead, often of rock crystal or onyx, used in a necklace as a spacer between contrasting stones.

This sums it up as rondelle beads are small and flatter than other beads and are useful as spacers.

They come in a huge range of colours, designs and material such as swarovski, glass and crystal.