Mordenite sprays within a vug
|(Ca, Na2, K2)Al2Si10O24·7H2O|
Mordenite is a zeolite mineral with the chemical formula, (Ca, Na2, K2)Al2Si10O24·7H2O. According to Ullmann's Encyclopedia of Industrial Chemistry (2005), it is one of the six most abundant zeolites and is used commercially.
Mordenite is orthorhombic (a,b,c unequal & all angles 90 degree). It crystallizes in the form of fibrous aggregates, masses, and 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 g/cm3. When it forms well developed crystals they are hairlike; very long, thin, and delicate.
Mordenite’s molecular structure is a framework containing chains of five-membered rings of linked silicate and aluminate tetrahedra (four oxygen atoms arranged at the points of a triangular pyramid about a central silicon or aluminium atom). Its high ratio of silicon to aluminum atoms makes it more resistant to attack by acids than most other zeolites.
Mordenite is one of the most abundant zeolites in altered volcanic deposits; it 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. It is also found in marine sediments, as in the Ural Mountains and in dikes where water has attacked and altered volcanic glasses, as on the Isle of Arran in Scotland.
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