Example – Tourmaline, NaFe3Al6(BO3)3(Si6O18)(OH)4

The name comes from the Sinhalese word “Turmali” or “Thoramalli”, which applied to different gemstones found in Sri Lanka.

Schorl refinement showing composition dependence of the tourmaline structure

Fortier, S.; Donnay, G.
Canadian Mineralogist (1975) 13, p173-p177




Na (green)
FeO6 octahedra (purple)
AlO6 octahedra (blue)
SiO4 tetrahedra (orange)
BO3 trigonal planar units (blue)


3D rotatable model of Tourmaline

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