Clear quartz crystal is the pure form of the mineral silicon dioxide. It is free of any impurity in the crystal lattice that might create colour, and forms long hexagonal crystals that's meet at a single point. Sources of quartz crystal can be found in most parts of the world. Ancient Greeks believed it to be ice that was so frozen it could never be thawed, crysallos being the Greek word for ice. Quartz crystal possess both piezoelectricity and pyroelectricity. Both of which had been covered in my blog Electric Gems (see link). Some quartz crystals are so sensitive that the heat and energy generated by certain individuals can cause the gem to vibrate and glow. 

Clear quartz is an excellent gemstone to use for meditating and aids spiritual development. It's the number one stone for crystal healing and divination, we've all heard of crystal balls, after all.