Amethyst is a transparent, coarse-grained variety of quartz.  Amethyst is valued as a semiprecious gem for its beautiful violet color.  Amethyst contains a little more Iron Oxide than any other variety of quartz, and its color probably is caused from the abundance of iron oxide.  If you heat amethyst, the color is removed or can change into the yellow of citrine.  Most commercial citrine is usually made in this manner of heating amethyst!

             There are notable deposits of amethyst in Brazil, Uruguay, Ontario, and North Carolina.  Amethyst is also known has the birthstone for people born in the month of February.  Amethyst is usually faceted with step cuts or emerald cuts but also has been used since ancient times for carved intaglios!