brewsterite-Ba: Ba(Al2Si6)O16.5H2O
brewsterite-Sr: Sr(Al2Si6)O16.5H2O
Tectosilicates (framework silicates), zeolite group
Crystal System: Monoclinic
Specific gravity: 2.32 to 2.45
Hardness: 5
Streak: Sr White
Colour: Ba: White, Colourless, Pale Pink; Sr: White

Metamorphic environments
Basaltic cavities

Brewsterite is a hydrothermal mineral deposited in druses lining cavities in basalt and schist; more rarely in hydrothermal veins in ore deposits (HOM, Dana).
Associated minerals include zeolites, calcite and quartz (HOM).


At the Marron Volcanics of the Olalla Area South-Central British Columbia, Canada, brewsterite casts after calcite (pseudomorphs) have been found at Yellow Lake (KL p268).
World-class brewsterite-Sr occurs in several spots along the Yellow Lake road cuts and at the White Lake Road site. Most common are translucent to transparent, white to slightly pinkish-tan, blocky to short prismatic crystals 1–5 mm long, but exceptional, blocky crystals to 1.5 cm wide have also been found here. Pale yellow calcite and heulandite coloured red by hematite inclusions are commonly intimately associated with the brewsterite-Sr. Less common associates are colourless fluorite octahedra, radiating groups of brown acicular goethite, white laumontite prisms and dark red to black prisms of lanthanum-bearing wakefieldite-(Ce) (R&M 96.6.520).

At the Blue Mountain Quarry, Methuen Township, Peterborough County, Ontario, Canada, Brewsterite-Ba occurs in cavities in prehnite as crystals and aggregates to 1 mm associated with quartz, diopside, calcite, wollastonite and microcline, as well as prehnite (Min Rec 37-4.288).

Brewsterite-Ba has two co-type localities, Cerchiara Mine, Borghetto di Vara, La Spezia Province, Liguria, Italy and Gouverneur Talc Company Number 4 Quarry, Diana Township, Lewis county, New York, USA.

Brewsterite-Sr has its type locality at Strontian, Highland, Scotland, UK.

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