Amethyst is the purple variety of quartz (SiO2), containing an impurity of iron, which gives the violet color to the mineral. The hardness of the mineral is the same as quartz's Technical details:SiO2 (Silicon Dioxide) Color:Crystals Transparent and Purple Hardness: 7 Density: 2.65 Where found:United States, England, Canada, Brazil, Mexico, Russia, Sri Lanka, Uruguay, East Africa, Siberia, India