Barrerite

Barrerite
Barrerite from Kuiu Island, Alaska, USA.
General
Category	Zeolite
Formula (repeating unit)	(Na,K,Ca)2Al2Si7O18·6(H2O)
Strunz classification	9.GE.15
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Amma
Identification
Color	White, pink
Cleavage	Perfect
Mohs scale hardness	3 - 4
Luster	Vitreous-glassy
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.13
Optical properties	Biaxial (-)
Refractive index	nα = 1.479 nβ = 1.485 nγ = 1.489
References

Barrerite is a tectosilicate mineral and a member of the zeolite family. It is one of the rarer zeolites. It was named for Richard Barrer, a New Zealand-born chemist.

Barrerite crystal are white to pinkish, with a vitreous-glassy luster. The crystal system is orthorhombic and is flat and tabular in appearance. It has a Mohs hardness of 3 to 4 and its cleavage is perfect. Barrerite has a white streak and a density of 2.13.

It was first described in 1974 for an occurrence in Sardinia at Sant' Efisio Tower on Cape Pula in Cagliari Province. It has also been reported from Rocky Pass, Kuiu Island, Alaska, and a few other localities.