An orthorhombic mineral, Ca₂Al₂Si₃O₁₀(OH)₂, in which Fe replaces Al; forms botryoidal or mammillary and radiating aggregates. Occurs in: hydrothermal veins, cavities, and amygdules in basalt; veins in felsic plutonic rocks; and low-grade metamorphic rocks. Commonly associated with zeolites.