406 



DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25, 



that this layer consists in some degree of reworked material. The 

 surface of this bed shows ripple marks. The predominant constitu- 

 ents which a macroscopic examination afTords are calcite, barite, 

 argillaceous material, limonite, manganese oxide, and pyrite. Out- 

 side of the nodular, oolitic, and fragmentary character of the layer. 



:^^^^- 



Fig. 27. Microphotograph of manganiferous red shale from 219 An ; 

 slide 277 ; enlarged 22 diam. a, calcite vein ; b, hematite spherule. 



very little additional information concerning this peculiar rock could 

 be gained microscopically (Fig. 27, Slide 277). The spherules are 

 of two kinds, hematite and carbonate, and they average about 48 

 microns in diameter. Non-ferruginous portions of the slide show a 

 groundmass of such fine-grained green material that very little could 

 be made of it. Hyolithes, sponge spicules, and shell fragments 

 partially or entirely replaced by calcite are a noticeable feature. 

 Barite as scattered blades partially replaced by chlorite and pyrite, 

 hematite as the chief constituent of the spherules, and carbonate are 

 the most abundant of the determinable constituents of the slide 

 (Fig. 28, Slide 278). 



