Na(Li,Al)3Al6(BO3)3Si6O18(OH)4Trigonal
Tourmaline
Na(Li,Al)3Al6(BO3)3Si6O18(OH)4
SilicatesChemical FormulaNa(Li,Al)3Al6(BO3)3Si6O18(OH)4
Crystal SystemTrigonal
Mohs Hardness7.5
Specific Gravity3.06
ColorBlack, brown, green, pink, blue, red
LusterVitreous
StreakColorless
CleavageNone
FractureConchoidal to uneven
Occurrence
Found in granite pegmatites and metamorphic rocks. Strongly pleochroic.