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Formula: Sr(Al2Si6)O16.5H2O
Tectosilicates (framework silicates), brewsterite subgroup of
the zeolite group,
strontium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.32 to 2.45
Hardness: 5
Streak: White
Colour: White
Environments
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).
Localities
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).
Brewsterite-Sr has its type locality at Strontian, Highland, Scotland, UK.
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