White earthy dickite mixed with other clay minerals. Specimen from Korea. (Photo by W. Cordua.)

Formula: Al2Si2O5(OH)4 Monoclinic


Dickite is a clay mineral having the same formula as kaolin, nacrite and halloysite but a different crystal structure. It is found intergrown with other clay minerals. It requires x-ray diffraction for positive identification, hence is easily overlooked. Dickite can occur in soils, shales, and as a hydrothermal precipitate.

IRON COUNTY: Dickite is found in pockets in soft hematite ore at the Montreal Mine (NE NE Sec. 33 T.46N R.2E) (Bayley and Tyler, 1960).

SAUK COUNTY: Dickite encrusts quartz crystals in the breccias on the west side of the Rock Spring Narrows, E 1/2 SE Sec. 29 T.12N R.5E (Dalziel and Dott, 1970).