For your consideration are these beautiful Selenite pyramids. They measure approximately 25-30mm and are sold by the piece.
Selenite is a cleansing stone. Draws away and purified negative energies and is powerful enough to reprogram other stones. It is a stone of mental clarity, expanding awareness and improving one's connection with the divine. It enhances intuition and aids meditation. It brings good luck and is very protective.
Chakra: Third Eye and Crown