Tourmaline

Tourmalines are complex borosilicates of aluminum and many other elements, mainly sodium, iron, magnesium or lithium. In nature, these elements in the crystal structures of tourmalines are represented in a variety of ways. Today the chemical composition distinguish 14 kinds of tourmaline (schorl, dravite, ELBAITE, welcome liddicoatit, buergerit, feruvit, chromdravit, foitit, magnesiofoitit, olenit, povondrait, rossmanit, vanadiumdravit). These are mixed with each other, so the correct assignment of a sample of turmaline to a particular species is usually possible only after a thorough chemical analysis, according to the predominant component. The chemical composition of tourmaline often changed during its growth. Tourmalines commonly have different chemical composition in the middle of the crystal and others at its edges, or differ in chemical composition at the ends of the columnar crystal and in the middle of the column. The most widespread tournaments are scorching, starving and elbait. Perfectly combines the lead with the predator (so-called skoryl-dravitová) and the skull with the elbaite (a series of skoryl-elbaitová).
Tourmaline forms acicular and columnar crystals longitudinally grooved in cross-section triangular or hexagonal, or stébelnaté forms, acicular or even felty aggregates. Tourmalines are glass-glossy to matt, on uneven to last-lasting fracture they are vitreous to greasy. They are transparent, translucent to opaque. Most common are black, brown, dark green, dark blue, or pink, red, light green, light blue, etc.