U. S. GEOLOGICAL SURVEY 



MONOGRAPH XIX PLATE XXIV 



Actinolite-magnetite schist. 



Fig. 2.— Actinolitic slate. 



Fig. 3.-Cherty iron carbonate. p,^ 4,_Cherty iron carbonate, in polarized light. 



THIN SECTIONS OF THE ACTINOLITIC SLATES FROM THE IRON-BEARING MEMBER OF THE PENOKEE SERIES, AND CHERTY IRON CAR- 

 BONATES FROM THE VERMILLION SERIES. 



