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Silicate

Heulandite-Ca

(Ca,Na,K)₅(Si₂₇Al₉)O₇₂·26H₂O
Hardness3.5–4
Crystal systemMonoclinic
ClassSilicate
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Heulandite-Ca specimen

crystals of heulandite-(Ca), crystals of mordenite : Mahodari, Nashik District (Nasik District), Maharashtra, India — Photo: Parent Géry · CC BY-SA 3.0

Heulandite-Ca

Also known as: Heulandite.

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.

Intro adapted from Wikipedia (CC BY-SA).

Heulandite-Ca is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ca,Na,K)₅(Si₂₇Al₉)O₇₂·26H₂O.

It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Heulandite structural group.

Key properties: Mohs hardness 3.5–4; typically white or pink or red or colorless or orange or yellow; white streak; vitreous luster.

IMA symbol Hul-Ca, IMA status: approved, named in 1822.

Collections: Collector Favorites.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data and a Wikipedia introduction — a full written entry hasn’t been published yet. Browse more H minerals or help write this entry.