Stilpnomelane is common in the Ironwood Iron formation mined through the Gogebic Range. Stilpnomelane is found as brown crystals in crude clusters as much as 3 mm. Stilpnomelane is found locally in the iron formation associated with the Duval massive sulfide deposit in sec. 2 and 3 T.35N. R.18E. and sec. It is associated with magnetite, pyrrhotite, grunerite and other amphiboles.
Associated minerals are epidote, quartz, chlorite and actinolite.
It is associated with chloritoid, biotite and actinolite.