412 



DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25. 



through the ore are irregular small areas of a pink carbonate re- 

 sembling rhodochrosite in physical characteristics, and barite. The 

 ore is incrusted with psilomelane as an oxidation product. Micro- 

 scopic examination brings out a coarsely banded and nodular struc- 

 ture with a groundmass of indeterminate material which is for the 

 most part homogeneous to all appearances and of brown color. 



Fig. 31. Microphotograph of barite sheaf in manganese oxide-carbonate 

 ore from 219 E4 ; slide 269 ; enlarged 22 diam. a, barite sheaf ; b, manganese 

 oxide-carbonate ore. 



The color of this ore is due to the brown and black oxides of 

 manganese and iron. Conspicuous among the anisotropic minerals 

 are barite which occurs as blades or bundles of blades generally 

 replaced by chlorite, and calcite, all very much discolored by the 

 manganiferous and ferruginous oxides. Minute veins of discolored 

 calcite are present (see Fig. 31, Slide 269). 



The chemical analysis of the ore and its recalculation are as 

 follows : 



