Tourmaline (etched)

A wonderfully blue partially gemmy heavily etched doubly terminated crystal with a small albite on one end.

Locality: Barra de Salinas, Minas Gerais Brazil

Composition: Being the tourmaline groups composition can vary widely the general chemical formula is X = Ca, Na, K, ▢ = vacancy. Y = Li, Mg, Fe²⁺, Mn²⁺, Zn, Al, Cr³⁺, V³⁺, Fe³⁺, Ti⁴⁺, vacancy. Z = Mg, Al, Fe³⁺, Cr³⁺, V. T = Si, Al, B.