Am'ethyst (ăm' ē-thĭst), a purple variety of rock crystal or quartz. Its name comes from the Greek, meaning "to prevent intoxication," and was given it because of the idea held by the ancients that liquor drunk from a cup made of amethyst would not intoxicate. It is found in Brazil, Ceylon, India and many other places, and is much worn in the form of rings, seals, etc. The oriental amethyst is a variety of the sapphire.