Mordenite is a rare zeolite mineral with the chemical formula, (Ca,Na2,K2)Al2Si10O24·7H2O. It is a zeolite. According to Ullmann's Encyclopedia of Industrial Chemistry (2005), it is one of the six zeolites, that occurs in the largest quantities and has a commercial presence at present.
Mordenite is orthorhombic. It crystallizes in the form of fibrous aggregates, masses, snd vertically striated prismatic crystals. It may be colorless, white, or faintly yellow or pink. It has Mohs hardness of 5 and a density of 2.1. When it forms well developed crystals they are hairlike; very long, thin, and delicate.
The mineral is found in volcanic rock such as rhyolite, andesite, and basalt. It is associated with other zeolites such as stilbite and heulandite. Good examples have been found in Iceland, India, Italy, Oregon, Washington, and Idaho.