It is a semiprecious stone and is the traditional birthstone for February. http://dictionary.reference.com/browse/amethyst
1250-1300; Latin amethystus, Greek améthystos not intoxicating, not
intoxicated (so called from a belief that it prevented
The ancient Greeks wore amethyst and made drinking vessels
decorated with it in the belief that it would prevent
intoxication. It is one of several forms of quartz.