Mordenite: Gemstone Information
Mordenite is (Na2 CaK2)4[Al8Si40O96]28H2O and an orthorhombic member of the zeolite group of minerals in which it forms compact fibrous aggregates with a perfect cleavage in one direction. Specimens may be colourless or stained yellowish or pinkish with hardness 3–4 and SG 2.12. The RI for the alpha, beta and gamma rays is 1.472–1.483, 1.475–1.485 and 1.477–1.487,biaxial positive or negative with birefringence 0.005. Mordenite occurs in veins and amygdules in various igneous rocks and may be found as an alteration of volcanic glasses. Mordenite is found at, among other places,Morden and along the Bay of Fundy, Nova Scotia, Canada.