Amethyst is a well-known variety of purple quartz. Its color can be from a touch of lavender to bright violet, depending on the iron amount in the quartz. It is common in geodes and is the main February birthstone, the other being onyx. The ancient Greeks and Romans believed wearing an amethyst would stop intoxication. The ancient Egyptians used amethyst for intaglios. Since the discovery of large amethyst deposits in Brazil it has lost its value as a cardinal gemstone. Amythest can also be heat treated to make amaythest.