Amethyst Gemstones Hardness 7.0. Appearance Violet, lilac or mauve quartz is called amethyst.
Amethyst is sometimes heat treated to form citrine .
Amethyst crystals can form together with citrine crystals to form bi-colored quartz called ametrine . Amethyst is the birthstone of the month of February. More information on gemstone enhancements. Prices are subject to change without notice. Actual carat weight may vary from the average carat weight listed.