Heulandite, named after the English mineralogist Heuland, is a mineral of the Zeolite family, often occurring in amygdaloid, in foliated masses, and also in monoclinic crystals with pearly luster on the cleavage face. It is a hydrous silicate of alumina and lime with the formulae (Na,Ca)4- 6Al6(Al, Si) 4Si26O72u24H2O and a relative hardness of 4. It is found in the cavities of basic igneous rocks and often associated with
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