Multi-Colored Tourmaline Classification
Variations Of Two, More Colors Usually Green, Blue, Red
Parti-Colored Tourmaline, Bi-Color Tourmaline, Tri-Color Tourmaline
appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity
Not all multi-colored tourmaline is elbaite tourmaline Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH).Dark material might have a birefringence as high as 0.040.Pyroelectric: development of opposite charges at the ends of a tourmaline crystal due to change in temperature. Piezoelectric: development of opposite charges at the ends of a tourmaline crystal when placed under stress.