Rock crystal is a colourless and transparent type of Quartz.
The name comes from the Greek "krystallos" meaning "ice".
Colourless Quartz can decompose light. They sort of mesmerise people, and thus have been renamed "stones of light". They are attributed the power to keep darkness away and to contribute to the emergence of positive energy.
Lithotherapists use it as a magnifier to strengthen and stabilize the effect of their charmstones.