Tourmaline
$(Na,Ca)(Li,Mg,Al)(Al,Fe,Mn)_6(BO_3)_3(Si_6O_{18})(OH)_4$
Family
cyclosilicates
Crystal system
rhombohedral
Color
black, red, brown, white,
Streak color
white
Cleavage
No cleavage
Hardness
7 to 7,5
Density
3,0 to 3,3
Explanations: →
Here
List of minerals: →
Here
