Formation
(1) Hydrothermally, through the alteration of calcium-rich plagioclases in basic igneous rocks (e.g., basalt and gabbro) under low-grade metamorphic conditions of the zeolite to prehnite-pumpellyite facies.
(2) As a fracture-filling mineral formed by the circulation of hydrothermal fluids within igneous or metamorphic rock bodies.
