Rock or "Mountain" crystal is the colorless variety of quartz and can be found all over the world Some crystal can weigh tons, but polishable quality is rather rare. The name "crystal" Is actually derived from the Greek "crystallos" It means "Ice", In those days rock crystal was believed to be eternally frozen water. Rock crystal is often used as imitation for diamond.
- Refractive index: 1.544-1.553
- Birefringence: 0.009
- Specific gravity: 2.65/ ±0.02-0.03
- Crystal system: Trigonal
- Hardness: 7
- Inclusions- Polariscope bull's eye