Amethyst is a variety of crystalline quartz in colors ranging from pale lilac to deep reddish purple and ranging from transparent to translucent is known as amethyst. Green amethyst is known as prasiolite, and is produced by heat treatment. Value per carat in violet purple amethyst, unlike many gems, doesn't rise exponentially with weight as it is readily available in large sizes; but depends almost entirely on color. "Siberian" deep purple amethyst with red and blue flashes commands the highest prices.
Purple amethyst is indeed one of the most classic gemstone types frequently used in gemstone rings. Amethyst is also very well suited for all other types of gemstone jewelry too, including gemstone earrings, pins and brooches, as well as in necklaces and fashionable gemstone pendants.