Reliquaries are containers used to protect and display relics. While frequently taking the form of caskets, they have many other forms including simulations of the relic encased within (e.g., a gilded depiction of an arm for a relic consisting of arm bones). Since the relics themselves were considered valuable, they were enshrined in containers crafted of or covered with gold, silver, gems, and enamel. Ivory was widely used in the Middle Ages for reliquaries; its pure white color an indication of the holy status of its contents. These objects constituted a major form of artistic production across Europe and Byzantium throughout the Middle Ages.