Selenite the Divine Light 
In the ancient world, Selenite protected against "wanderings of the mind". It invokes mental clarity and Divine inspiration.
Such a powerful crystal it never needs cleansing itself as it can cleanse and charge your other crystals.  Cut cords of unwanted energies from others by scanning it across your body. 
Place my the side if your bed to help with an overactive mind. Named after Selene the Goddess of the Moon for its moon bean like look shining Divine light on the earth.