... glass, plastic, and actual mollusc shell. Some beads are coated with a pearlescent substance in order to imitate the natural iridescence ... mixture of plastic enamel, lead carbonate, mica, and titanium dioxide, then with a film of iridescent nylon.Bohemian pearl: cut and ... pearl simulants are hollow glass beads coated with essence d'orient and filled with wax. Variations of these wax-filled simulants ...