3.5mm to 6.5mm Rainbow Calsilica PlainRondelle Beads are a beautiful man-made stoneformed fromcalcite carbonate rock set in resin,is color enhanced and stabilized for durability. These gems are striated with vibrant colors giving them their name. The beads have a waxy luster, are opaque, have a symmetrical rondelle shape, and are graduated on the strand.