These bracelets are easy to mix and match and are made with stretch cord for an easy fit. Since black tourmaline is pleochroic, it might also be green when viewed along a different axis. This crystal is also piezoelectric which means that through mechanical action an electric pulse is formed, similar to quartz. Tourmaline is sought after as a talisman of protection to deflect and counteract negative energies. It is also used to guard against radiation and environmental pollutants.