apophyllite

noun

1. a hydrous potassium and calcium silicate mineral occurring in white crystals.

noun

1. a white, colourless, pink, or green mineral consisting of a hydrated silicate of calcium, potassium, and fluorine in tetragonal crystalline form. It occurs in cracks in volcanic rocks. Formula: KCa 4 (Si 4 O 10) 2 (OH 1 F).8H 2 O