How does tourmaline generate negative ions?
It is thought that the surface of tourmaline is electronically charged when pressure is applied to it or when temperature changes and then the electronic charge ionizes the air. Tourmaline generates little amount of negative ions when no external force is applied to it because it is electronically neutral. Actually, it is electronically charged as friction is applied to it by the atmospheric pressure and the surrounding air but the electronic charge is cancelled out by ions floating in the air. The piezoelectric effect is a phenomenon where tourmaline is electronically charged when pressure is applied to it. The pyroelectric effect is a phenomenon where tourmaline is electronically charged when temperature changes.
