(Sr,Ba,Ca)(Al₂Si₆)O₁₆.5H₂O

This sample of Brewsterite is displayed in the Smithsonian Museum of Natural History. Brewsterite is an aluminum silicate of the zeolite group which contains strontium and barium. Its composition is (Sr,Ba,Ca)(Al₂Si₆)O₁₆.5H₂O. The sample at left is about 5x5 cm and is from Whitesmith mine, Strontian, Argyll, Scotland.