Heulandite-Ba
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-Ba is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ba,Ca,K)₅(Si₂₇Al₉)O₇₂·22H₂O.
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; specific gravity 2.35; White streak; Vitreous, pearly on {010} cleavage surfaces luster; optically biaxial.
IMA symbol Hul-Ba, IMA status: approved, named in 2003.
A late stage mineral in hydrothermal quartz-calcite veins.
It is found associated with Acanthite, barite, chalcopyrite, fluorite, galena, sphalerite, silver, brewsterite, other heulandite-series zeolites, calcite, harmotome.
The name refers to its chemical composition and relationship to other heulandite minerals.