White fibrous halotrichite from Golden Queen Mine, Kern County, California. Field of view is about 5 cm. left to right. (Photo by W. Cordua.)

Formula: FeAl2(SO4)4.22H2O  MONOCLINIC


Halotrichite usually forms as crusts on sulfide minerals during weathering. It is a water soluble mineral that does not survive long in Wisconsin’s climate.

RUSK COUNTY: White fibrous crystals of halotrichite were abundant as post-mining deposits on rock surfaces in the Flambeau Mine, Ladysmith. (Cordua, 1995, field notes).