Skull; humans have been using skulls to deepen their meditations for centuries. Look into their eyes and focus on what you want. 
 
The Mediation and Attunement Stone
It is the most powerful healing stone of the mineral kingdom, able to work on any condition. Clear Quartz is known as the stone of power and amplifies any energy or intention. Clear Quartz protects against negativity, attunes to your higher self, and relieves pain.  It has the same DNA make up as human.