WGNHS
Wisconsin Geological and Natural History Survey

Saponite

Yellow-green masses of saponite on quartz. From the Isle Royale Mine, Houghton, Michigan. Field of view is about 0.5 cm. Specimen is in the University of Wisconsin–River Falls collection. (Photo by W. Cordua.)

Formula: Ca0.25(Mg,Fe)3(Si,Al)4O10(OH)2.nH2O Monoclinic

Description:

Saponite is a clay mineral most often found as an amygdule filling in volcanic rocks.

DOUGLAS COUNTY: Saponite is reported as occurring in the amygdules of basaltic volcanic rocks exposed along the Black River (Irving, 1883).