BREWSTERITE

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Monoclinic
    Chemistry : (Sr,Ba,Ca)Al2Si6O16 5H2O
    Rarity : Rare

Brewsterite is a rare zeolite that occupies the cavities of basalts and shales, often in the company of calcite. It is also sometimes a zeolite from hydrothermal veins and exceptionally nepheline syenite. Its name was given to it in honor of the Scottish physicist and mineralogist Sir David Brewster. It occurs in isometric or prismatic crystals, striated and elongated, not exceeding 1.5 cm, often grouped in rosettes or fibroradiated aggregates. It is usually colorless or white, it can sometimes be colored yellowish or greenish.

Main photo : Brewsterite from Whitesmith mine, Strontian, Scotland, UK © John Sobolewski

Brewsterite from Gamlegrendasen, Kongsberg, Norway © Oivind Thoresen
Brewsterite from Barèges, Hautes-Pyrénées, France © Laurent Gayraud
Brewsterite from Yellow Lake, British Columbia, Canada © Antonio Zordan
Brewsterite from the Invernet glacier, Savoie, France © Luigi Chiappino

Brewsterite in the World

The finest known brewsterite crystals come from the Strontian district in the Scottish Highlands. It is also mentioned in the alkaline massif of Burpala, near Irkutsk (Siberia).

Brewsterite in France

In France, brewsterite is present in good crystals in the alpine clefts around Bourg d'Oisans (Isère). Brewsterite is also reported in the Pyrenees, near Gèdres and Barèges.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fake recorded for this mineral species.


Hardness : 5
Density : 2.5
Fracture : Irregular
Trace : White

TP : Translucent to transparent
RI : 1.512 to 1.530
Birefringence : 0.014
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None