U. S. GEOLOGICAL SURVEY 



BULLETIN 583 PLATE IV 



A. CUT AND POLISHED CRYSTAL OF BROWN FERBERITE. 



From Winnebago claim near Rollinsville, Colo. Shows spongy structure of theferberite, the pores of which 

 are filled with hydrous iron oxide. X 78. 



B. BRECCIATED FERBERITE VEIN. 



From the Conger mine, Nederland, Colo. Both the black and the gray edging it are ferberite, the differ- 

 ence in color being due to the orientation of the crystals. Natural size. 



