Heulandite
heulandite series, zeolite
Heulandite is the name of a series of tectosilicate minerals of the zeolite group. Prior to 1997, heulandite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named:
Heulandite-Ca
Heulandite-Na
Heulandite-K
Heulandite-Sr
Heulandite-Ba (described in 2002).
Heulandite-Ca, the most common of these, is a hydrous calcium and aluminium silicate with the formula (Ca,Na)5(Si27Al9)O72·26H2O. Small amounts of sodium and potassium are usually present replacing part of the calcium. Strontium replaces calcium in the heulandite-Sr variety. The appropriate species name depends on the dominant element. The species are visually indistinguishable, and the series name heulandite is still used whenever testing has not been performed.
Crystallography and properties
Crystals are monoclinic. They may have a characteristic coffin-shaped habit, but may also form simple rhombic prisms. Frequently, a crust of fine crystals will form with only the ends of the rhombs visible, making the crystals look like wedges. They have a perfect cleavage parallel to the plane of symmetry, on which the lustre is markedly pearly; on other faces the lustre is of the vitreous type.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jan 31, 2026. The linked authority identifier is Q1466985. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1997 and 2002.
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This entry incorporates text from “Heulandite” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.