Tourmaline
(toor'-ma-lin')
18th c.; sinha. touramalli
Complex crystalline silicate containing aluminum, boron, and other elements, used in electronic instrumentation and, especially in its red, green, and blue varieties, mounted in jewelry
Family
Complex silicate of aluminum and boron
Chemical composition
(Na,Ca)(li,Mg,Al)3Al6B3Si6O27(OH,F)4 + others metals
Hardness (Mohs scale)
7 - 7,5
Specific gravity
3,10 ±0,10
Refractive index
1,624 - 1,644 ±0,006
Optical character
Uniaxial -