Amethyst One of the most celebrated quartz gems is amethyst. Adopted as the official gemstone of South Carolina and Ontario in 1969 and 1975, it is merely purple quartz. Amethyst's long popularity among royalty is due partly to the status of purple as a royal color, along with amethyst's great beauty. In fact, amethyst would be much more expensive if it weren't so common. Indeed, more expensive gems are often compared to amethyst.
Some quartz is made of crystals too small to be seen with the naked eye.
Such material is called cryptocrystalline quartz. Cryptocrystalline quartz includes chalcedony or agate. Mozarkite Missouri's official state rock is mozarkite, a crypto-crystalline variety of quartz blended with agate and jasper, beautifully patterned in ripples and ribbons. It has a hardness of 7 and is suitable for cutting and polishing. Mozarkite is found in the Ozark region of Missouri as far north as Marshall and is abundant in Benton and nearby counties.