gS NEW YORK STATE MUSEUM 



With this amount of manganese in the same formations and not 

 far distant, and the significant coincidence of the association of the 

 bogs with this formation, it seems reasonable to suppose that the 

 metamorphosed Ordovician and possibly lower Silurian formations 

 are the ultimate source of the manganese which has given rise to the 

 concentrated derivatives in the form of bog manganese or wad in 

 the high bogs of the western foothills of the Taconic range in Colum- 

 bia county. 



The only evidence of the occurrence of some form of manganese in 

 these formations was shown in the 19 17 Spencertown-Austerlitz 

 state road cutting near Spencertown where the schists and slates 

 were discolored by the dioxide. The Rensselaer grits, east of this 

 locality, were intrically veined with pink orthoclase, chlorite and 

 quartz unaccompanied by any manganese staining. 



In the vicinity of Canaan on the Girdler farm, numerous specimens 

 of cavernous quartz as evidence of the work of solution were found, 

 but whether the original mineral filling the cavities was calcite or 

 rhodochrosite could not be determined, though the cavities were 

 lined with the powdery black dioxide of manganese. 



For the reasons given above, the writer believes that the rocks 

 underlying the drainage areas are in all probability the ultimate 

 source of the manganese. The decomposition of the silicate minerals 

 no doubt was brought about by carbonic acid and the " so-called 

 humic sols, the latter consisting of about 50 per cent C, 43 per cent 

 O, 4.5 per cent H, 2 per cent N and some O and S found in large 

 amounts in marshy water." 



On the J. Goodsell bog, which contained the highest amount of 

 manganese, a thin film of dark greenish and bluish iridescent coating 

 was found quite like the iridescent coating found in connection with 

 bog limonite and iron springs, but unlike it so far as the darker 

 degree of color is concerned. According to Beyschlag, Vogt and 

 Krusch (2:986) "The humic sols are not precipitated by ferrous 

 but by ferric salts. When a solution containing ferrous salts meets 

 one containing humic sols, a soluble ferro-humate is first formed 

 which upon oxidation passes gradually over to ferri-humate. This 

 is in fact immediately precipitated, forming there the thin, often 

 iridescent coating which when present in spring courses indicates 

 the ferruginous character of the water." If upon examination any 

 of the iridescent scum of manganese bogs proves to contain manga- 

 nese in large amounts, such an origin as conveyed by the foregoing 

 quotation might very well indicate similar origin for the manganese. 



