Amethyst

Crystalline quartz in shades of purple, lilac or mauve are called amethyst. Amethyst is dichroic, showing a bluish or reddish purple tinge when viewed from different angles. Usually faceted as a mixed- or step-cut, amethyst has distinctive inclusions, which look like tiger-stripes, thumbprints or feathers. Amethyst has long been called the "sobriety stone." In ancient Rome, crushed amethyst gem stone beads were added to wine cups to prevent drunkenness.