What is Amethyst, Properties, Color, Cut, Clarity, and Benefits The amethyst gem is found in colors such as violet, purple, purple-white, and dark purple which in essence is a quartz mineral. Chemically, the amethyst stone is made up of a compound known as silicon dioxide. It has been found that about 59% of the earth’s crust consists of silica, which is why silica is considered a very abundant mineral. Some of the other gemstones of the quartz family include black onyx, green onyx, Citrine, moss agate, and dendritic agate.