Ca₂Al(Si,Al)₄O₁₀(OH)₂

This sample of prehnite is displayed in the Smithsonian Museum of Natural History. Prehnite is a silicate mineral with the composition Ca₂Al(Si,Al)₄O₁₀(OH)₂. The sample at left is about 8 cm across and is from Calvinia, Cape Province, South Africa.

This sample of prehnite is from Bombay, Maharashtra, India. It is about 20 cm wide and is described as prehnite after laumontite.

This prehnite sample is about 15 cm across and is from Prospect Park, New Jersey. It is described as prehnite with calcite.

This sample of prehnite is from Jeffrey mine, Asbestos, Quebec, Canada. It is about 18 cm wide.

This prehnite sample is about 10 cm across and is from Patterson, New Jersey. It is described as prehnite with calcite.

This sample of prehnite is from Patterson New Jersey. It is about 20 cm wide.

This is about one quarter of the prehnite sample above that is about 40 cm across and is from Fairfax quarry, Centreville, Virginia. It is described as prehnite with fluorapophyllite.

This sample of prehnite is from Jeffrey mine, Asbestos, Quebec, Canada. It is about 12 cm wide.

This large sample is from Khandivalli quarry, Bombay, Maharashtra, India. It is described as prehnite with gyrolite and fluorapophylite. It is probably about 25 x 40 cm.