A mineral inosilicate with composition Ca₂NaSi₃­O₈ (OH), crystallising in the triclinic system. Crystals are usually acicular in radiating aggregates (see illustration). There is perfect cleavage parallel to the front and basal pinacoids yielding splintery fragments elongated on the b crystal axis. The hardness is 5 on Mohs scale, and the specific gravity is 2.75. The mineral is colorless, white, or grey with a vitreous to silky luster. Pectolite, a secondary mineral occurring in cavities in basalt and associated with zeolites, prehnite, apophyllite, and calcite, is found in the United States at Paterson, Bergen Hill, and Great Notch, New Jersey.