Barrerite

barrerite

heulandite

zeolite

Kuiu island

Images

Formula: Na₂(Si₇Al₂)O₁₈.6H₂O
Tectosilicate (framework silicate), stilbite subgroup, zeolite group
Crystal System: Orthorhombic
Specific gravity: 2.3 measured, 2.08 calculated
Hardness: 3 to 4
Streak: White
Colour: White, pink
Common impurities: Ca,K,Fe,Mn,Mg,Sr,Ba
Environments

Volcanic igneous environments

Localities

At the type locality, the Sant' Efisio Tower, Capo di Pula, Pula, Metropolitan City of Cagliari, Sardinia, Italy, barrerite occurs as well-formed, laminar crystals to 5 mm, on the walls of large fractures in deeply weathered andesitic and rhyolitic lavas, associated with heulandite (HOM).

At Hound Island, Petersburg Borough, Alaska, USA, barrerite is very rare in the calcium-rich Triassic (252-201 million years ago) breccias (CM 35.691-698).

At Kuiu Island, Petersburg Borough, Alaska, USA, barrerite crystals up to several centimeters in length, accompanied by microcrystalline quartz in characteristic stalactite-like dendritic aggregates, line vugs as wide as several decimeters. Barrerite crystals and quartz aggregates overgrow one another, probably as the result of several sequences of altemating crystallisation (CM 35.691-698).

Rocky Pass, Petersburg Borough, Alaska, USA, is a narrow and shallow area separating the islands of Kuiu and Kupreano. It features pillow basalt having the characteristic texture of lavas solidified under water or ice.
Zeolite-containing vugs have been exposed in the tidal area. Barrerite is restricted to this tidal area, and is probably formed by crystallisation in the presence of seawater (CM 35.691-698).

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