*phyllite*

n. [ Pref. apo- + Gr. &unr_; 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. [ 1913 Webster ]

n. [ Gr. 'asth`r star + fy`llon leaf. ] (Paleon.) A fossil plant from the coal formations of Europe and America, now regarded as the branchlets and foliage of calamites. [ 1913 Webster ]

n. [ See Phylo-. ] (Min.) (a) A mineral related to ottrelite. (b) Clay slate; argillaceous schist. [ 1913 Webster ]