Precious stones have been thought of as objects that can aid in healing—in a practice known as lapidary medicine—by a variety of cultures. The Hopi Native Americans of Arizona use quartz crystals to assist in diagnosing illnesses. Both Pliny the Elder and Galen claimed that certain crystals had medicinal properties. In Europe, the belief in the healing powers of crystals (and in particular crystal amulets) persisted into the Middle Ages. The alleged medicinal properties of precious stones, as well as other powers they were believed to hold, were collected in texts known as lapidaries, which remained popular in Medieval and Early Modern Europe until the 17th century.