The ferrierite group of zeolite minerals consists of three very similar varieties: ferrierite-Mg, ferrierite-Na, and ferrierite-K, based on the dominant cation. Ferrierites are orthorhombic minerals with highly variable cationic composition, (Na,K)2Mg(Si,Al)18O36(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, they come from Kamloops Lake, BC, Canada and Leavitt Lake, California. Ferrierite was named for Canadian geologist and mining engineer Walter Frederick Ferrier (1865-1950).
Synthetic ferrierites have even greater cation variability and have important uses as commercial filters and ion-exchange beds.