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DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25, 



Under the microscope a thin section of this bed reveals hematite in 

 the form of a pigment and as grains and ill-formed spherules, 

 while local areas of carbonate are found. The upper member of 

 this bed, 219 A 4b 3 is a red shale containing small subspherical and 

 'discoidal nodules quite similar to those described in detail above. 



219 A 5 is a nodular ferruginous shale which is calcareous and 

 manganiferous. The shaly structure and the manganese are brought 

 out in a conspicuous way through weathering; the manganese by the 

 black discoloration in evidence as one of the derived oxides. This 

 bed has a thickness of .2 of a foot but thins and thickens, presenting 

 a lenticular appearance. The nodules, or possibly pebbles, are sub- 

 spherical in form, dark green in color, and of impalpable fineness of 

 grain. They resemble those already described in connection with the 



Fig. 21. Photograph of poHshed vertical section of banded manganese 

 carbonate-oxide ore from 219 A7, natural size, a, green band ; b, red band ; 

 c, barite. 



