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).