402 DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25, 



The brown band differs in chemical composition, in color, and in 

 specific gravity. The color is a light or dark chocolate brown. The 

 specific gravity is 3.32. The chemical composition differs mainly 

 in the higher percentage of manganese, as shown in the following 

 analysis : 



Analysis D. Analysis D 1. 



Brozvn Band. Recalculation. 



SiOo 10.23 MnO 28.93 



Fe,03 1-32 MnCOs 32.89 



FeO 89 CaCOo 14.01 



ALO3 484 MgCoa 5.90 



MnO 4925 2H,0-AL03-2SiO, 11.08 



CaO 8.1 1 SiOo 5.40 



MgO 3.02 Fe.Oj 1.27 



H2O 1.31 ^8 



CO, .; 21.83 



100.80 



Members b and c of bed 219 A 7 differ from the subdivision just 

 described in the greater abundance of jaspery bands in comparison 

 with the red shaly band and they show greater continuity on the 

 whole. 



Member d consists of green and brown jaspery bands all more or 

 less nodular and interlaminated with the red manganiferous shale. 

 Barite as segregations, disseminated blades, and veins occur infre- 

 quently. In the weathered portions of the section this bed is found 

 altering on its more exposed structural planes to the secondary 

 oxides of manganese such as psilomelane, etc. 



219 A 8 is a purplish manganiferous nodular shale measuring 0.3 

 of a foot in thickness. It contains lenticles and discoidal nodules 

 of the green jaspery manganese carbonate (Fig. 24, Slide 284). 

 The noticeable microscopic features of a thin section of this rock are 

 its nodular, oolitic and shaly structures. The spherules, though 

 rudely formed, are of either hematite or a carbonate, the former 

 more closely associated with the green jaspery structures, and the 

 latter with the red shale. 



219 A 9 is a manganiferous bed structurally, mineralogically, and, 

 presumably, chemically, analogous to 219 A 7, and measuring .5 of a 



