A violet, crystalline variety of quartz, amethyst is the birthstone for February. When of good color and transparency, it is valued as a semiprecious gem. Such stones normally are step-cut or intaglio-carved. It occurs in cavities in many rock types and is found in the Ural Mountains, Brazil, Sri Lanka, and the United States. Ancient Greeks attributed various powers to amethyst, particularly that of protecting against drunkenness and passion.