What is "glaucophane"

Glaucophane \Glau"co*phane\, n. [Gr. glayko`s silvery, gray + fai`nesqai to appear.] (Min.) A mineral of a dark bluish color, related to amphibole. It is characteristic of certain crystalline rocks.

n. (context mineral English) A mixed aluminate of sodium, magnesium and aluminium that has a characteristic blue colour, and exhibits pleochroism, with the chemical formula sodium₂(magnesium,iron²⁺)₃aluminum₂silicon₈oxygen₂₂(Ohydrogen)₂.

Glaucophane is the name of a mineral and a mineral group belonging to the sodic amphibole supergroup of the double chain inosilicates, with the chemical formula ☐Na(MgAl)SiO(OH).

Glaucophane crystallizes in the monoclinic system.