Amethyst
Amethyst is a variety of purple quartz that, when heated, changes color to yellow and is then called citrine (by artificial heat treatment). Its name derives from the Greek "amethystos", meaning "not drunk", in reference to its supposed virtues which protected against drunkenness. Highly prized since Antiquity, it has adorned many jewels over the centuries, notably bishop's rings, imposing religious jewels. Its shades range from mauve to violet deep.