The Collaborative International Dictionary
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.
Wiktionary
glaucophane
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.