Amethyst is the purple variety of quartz. It is an extremely popular gemstone and is the birthstone for February. Amethyst comes in a wide range of purple colors and is a very durable gem with a hardness of 7 on the mohs scale. Amethyst has a trigonal crystal system with a refractive index of 1.544 to 1.553. More information on the history and lore of amethyst is available here. Click here to see our finished Amethyst Jewelry.