i am colorful
i am a gemstone
i am a mineral
Na(Mg,Fe,Li,Al) 3 Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 4
The structure of tourmaline consists of sixfold rings of silicon tetrahedra that are stacked with BO 3 groups between the rings to form columns parallel to the c-axis. The Na resides in the center of the rings and the Mg and related elements are located along the inside edge of the rings. The stacks of rings are tied together laterally through Al in distorted octahedral coordination.
As implied by the formula above, there is a great deal of composition variation possible in tourmaline.
