(mineralogy) A mineral, of a white color and vitreous luster, with the chemical formula CaAl₂Si₄O₁₂·4H₂O. It is a hydrous silicate of alumina and lime. Exposed to the air, it loses water, becomes opaque, and crumbles.
tourmaline
tourmaline
noun
(mineralogy) A complex black or dark-coloured borosilicate mineral, compounded with various chemical elements and considered a semi-precious stone.
