U. S. GEOLOGICAL SURVEY 



MONOGRAPH XIX PLATE XXIII 



Fig. 1. — Ferruginous chert. 



Fig. 2. — Ferruginous chert, in polaiized light. 



f'g 3.— Actinolitic schist. Fig. 4.— Actinolittc schist, in polarized light. 



THIN SECTIONS OF FERRUGINOUS CHERTS AND ACTINOLITIC SLATES FROM THE IRON-BEARING MEMBER. 



