The ferrierite group of zeolite (the FER structure) consists of three very similar species: ferrierite-Mg , ferrierite-Na , based on the dominant cation in the A location. ferrierite-Mg and ferrierite-K are orthorhombic minerals and ferrierite-Na is monoclinic with highly variable cationic composition (Na,K) 2Mg(Si,Al) 18O 36(OH)·9H2O. Calcium and other ions are often also present. They are found in vitreous to pearly, often radiating, spherical aggregates of thin blade-shaped transparent to translucent crystals.
Ferrierite typically occurs as an alteration mineral in basaltic rocks and in tuffaceous sediments. In North America, it is found at Kamloops Lake, BC, Canada (the original type locality ) and Leavitt Lake, California. Ferrierite was named for Canadian geologist and mining engineer Walter Frederick Ferrier (1865–1950).