A bea is a small, decorative object that is pierced for threading or stringing. Beads range in size from under a millimeter to over a centimeter or sometimes several centimeters in diameter. Glass, plastic, and stone are probably the most common materials, but beads are also made from bone, horn, ivory, metal, shell, pearl, coral, gemstones, polymer clay, metal clay, resin, synthetic minerals, wood, ceramic, fiber, paper, and seeds. A pair of beads made from Nassarius shells that are approximately 100,000 years old are thought to be the first known examples of jewellery.