Amethyst is purple quartz and is one of the most popular gemstones. It varies from pale lavender ("Rose-de-France" amethyst) to deep purple with red highlights ("Siberian" amethyst).

 Amethyst is generally abundant and quite inexpensive (pennies to a few dollars per carat), although fine, large Siberian amethyst is rather scarce and may command prices of several tens of dollars per carat.

 When exposed to strong sunlight for extended periods, amethyst may fade in color. Recently, gem markets have been flooded with inexpensive synthetic amethyst. Although such synthetics can usually be identified by testing for twinning, routine testing is not cost-effective, and some new synthetics do not show the twinning effect.