Apophyllite

A‐poph″yl‐lite (�), n. [Pref. apo- + Gr. � leaf; so called from its foliated structure or easy cleavage.] (Min.) A mineral relating to the zeolites, usually occurring in square prisms or octahedrons with pearly luster on the cleavage surface. It is a hydrous silicate of calcium and potassium.