WGNHS
Wisconsin Geological and Natural History Survey

Ferrimolybdite

Bright yellow ferrimolybdite forming as alteration product of gray metallic molybdenite, with white quartz. Scale is in centimeters. (Photo by W. Cordua.)

Formula: Fe2(MoO4)3.n(H2O) Orthorhombic

Description:

Ferrimolybdite forms yellow earthy to fibrous coatings as a result of the oxidation of molybdenite.

FLORENCE COUNTY: Found at the Payant-Chrissman prospect pits in the north central part of sec. 33 T.38N. R.19E, about 6 km. south of Aurora. It is found with hematite coating molybdenite, pyrite and red K feldspar in altered pegmatite. (Greenberg, 1983).

MARINETTE COUNTY: Found at the Camp Five (Middle Inlet) molybdenite prospects in the SW NW sec. 18 T.33N. R.20E. Here it is found with hematite and occasionally fluorite in “smaller segregations in the granite and along some of the vein – fracture walls”. (Greenberg, 1983).