Clear Quartz is known as the Master Healer.  It's all about spiritual growth and is a powerful stone that absorbs, stores, releases and controls energy.  It increases mental clarity, concentration and focus.  It revitalises your emotional, mental, physical and spiritual planes and enhances your psychic abilities.  It's also a great amplifier for the energy of other crystals which is why it's primarily used in crystal grids
 
Chakra: Crown