Amethyst is a variety of the quartz, or silica group, one of the most widespread minerals on the face of the earth. However, superior examples that are suitable for faceting into gems are limited to relatively few regions. Amethyst crystals can form in a variety of different situations: as geodes in gas cavities of lava flows, in pegmatite veins or in metamorphic rocks. In only a few instances does Amethyst form as elongated prismic rock crystal; it normally forms small thick crystals with six-sided terminations.

Amethyst can range in color from pale lilac to an intense, almost black purple with red flashes, the latter of which commands the highest prices. The color in Amethyst is due in part to the presence of ferric iron impurities and color centers linked to natural radiation. Amethyst's principal mining locations are in Brazil, Uruguay, Russia, Zambia, India, Sri Lanka, Mexico and the U.S.