Artificial and imitation gems are of various kinds. Synthetic stones are made in the laboratory of the same chemical elements as natural stones. Among the synthetic gems produced commercially are rubies, sapphires, diamonds, emeralds, and spinel ' s.
Imitation pearls are glass or plastic beads coated with a preparation made from fish scales. A cultured pearl is made by inserting a small bead inside the oyster; the irritation causes the oyster to deposit pearly material upon the bead, leading to the formation of a pearl.