- Color: violet, purple-violet
- Hardness: 7
- Refractive index: 1.54 - 1.55
- Density: 2.65 - 2.66
- Chemical composition: SiO2
- Crystal structure: hexagonal
- Lustre: vitreous
- Origins: Widespread; main sources are Brazil, Uruguay, Bolivia, Argentina, USA, East Africa, Zambia, Namibia, Madagascar, India, Sri Lanka, Russia, Australia.
Amethyst is a transparent purple-violet variety of quartz. The best amethysts have a medium dark violet color and uniform coloring. They are rarely heated to lighten dark colors or to improve transparency. An amethyst will change color to yellow or greenish yellow after heat treatment. Long time exposure to direct sunlight may make the color fade.