Apophyllite Series

White to pink apophyllite with calcite and prehnite, on joint surface cutting gabbro. Buckley Quarry, near Amnicon Falls State Park, Douglas County, Wisconsin. (Image by W. S. Cordua.)

Formula: KCa4Si8O20(F,OH).8H2O Tetragonal


Apophyllite series minerals form from low temperature hydrothermal fluids. It is particularly common in veins within gabbros and basalts.

DOUGLAS COUNTY: White to pink cleavage masses and crude platy crystals several centimeters across occur with prehnite in veins cutting gabbros in the Buckley Quarry, near Amnicon Falls (NW Sec. 32 T.48N. R.12W.) (Cordua, 1991).