Tourmaline is the most multicolored mineral type known, occurring in virtually every color of the spectrum. It has many interesting optical properties. When viewed through their vertical axis, some specimens appear darker or differ in color than when seen through their horizontal axis. Certain Tourmalines exhibit a cat's eye effect when polished. This mineral 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.
Beautiful and useful too! Pendulums are used much the same way as applied kinesiology or muscle testing to help determine the answer to a question.