Agate

A semiprecious type of quartz also known as chalcedony (pronounced kal-sed-nee). It forms in a wide variety of colors and textures. Each individual agate forms by filling a cavity in a host rock. Agate was highly valued as a talisman or amulet in ancient times. It was said to quench thirst or protect from fevers. Persian magicians used agate to divert storms.