Amethyst

**Chemical composition:** SiO₂

**Hardness:** 7

**Density:** 2.6 g/cm³

**Crystal system:** α-quartz: Trigonal Trapezohedral class; β-quartz: Hexagonal

**Luster:** Vitreous

**Info:** Amethyst is a popular gemstone variety of quartz that ranges from a bright to dark or dull purple colour. It forms mostly columnar, hexagonal crystals in geodes occuring in alkaline magmatic rocks. The world's largest deposits can be found in Brazil, Mexico, Russia and Morocco.