MORDENITE, MONO LAKE, BRITSH COLUMBIA, CANADA (miniature)

Mordenite is a zeolite mineral characterized by the chemical formula (Na2,Ca,K2)4(Al8Si40)O96·28H2O, ranking among the six most prevalent zeolites used in commercial applications. First identified in 1864 by Henry How, it was named after the community of Morden in Nova Scotia, Canada, where it was initially discovered. This mineral exhibits an orthorhombic crystal system, forming fibrous aggregates, masses, and prismatic crystals that are often vertically striated. Its coloration can range from colorless to white, with possible faint yellow or pink hues. Mordenite has a Mohs hardness of 5 and a density of 2.1 g/cm3, with well-formed crystals appearing hairlike—long, thin, and delicate. The molecular structure of Mordenite consists of a framework featuring chains of five-membered rings formed by linked silicate and aluminate tetrahedra, which contributes to its higher resistance to acid attack compared to many other zeolites due to its elevated silicon-to-aluminum ratio. Mordenite is commonly found in altered volcanic deposits, particularly in volcanic rocks such as rhyolite, andesite, and basalt, and is often associated with other zeolites like stilbite and heulandite. Notable occurrences have been documented in regions including Iceland, India, Italy, Oregon, Washington, and Idaho, as well as in marine sediments in the Ural Mountains and in dikes where volcanic glasses have been altered by water, such as on the Isle of Arran in Scotland.