U. 6 GEOLOGICAL SUfiVEV 



MONOGRAPH XIX PLATE XXV 



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Fig. ].— Cheity iron cikL 



Fig. 2,— Sidentic chert. 



Fig. 3,— Actinoiite-sidente alate. Fig, 4.— Actinolite-siderire slate, in polarized light. 



THIN SECTIONS OF SIDERITIC SLATES FROM THE ANIMIKIE SERIES. 



