an Entity references as follows:
The ferrierite group of zeolite minerals (the FER structure) consists of three very similar species: ferrierite-Mg, ferrierite-Na, and ferrierite-K, 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)18O36(OH)ยท9H2O. 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.