236 ECONOMIC GEOLOGY 



according to F. W. Clarke do not represent igneous segregations. 

 They may have been leached out from their accompanying erup- 

 tive rocks, or may have been brought up from below. The sul- 

 phate and carbonate of cobalt are secondary minerals. Erythrite 

 arises from the oxidation and hydration of the arsenides and is a 

 common mineral in the oxidized zone of ore bodies bearing 

 cobalt as arsenides in the lower levels. Asbolite is an alteration 

 product of cobaltiferous ores and in many respects closely resem- 

 bles wad, or bog manganese. 



Character of the Ore Bodies. The principal ores occur in well- 

 defined fissure veins traversing both intrusives and much-altered 

 sedimentaries. The chief gangue mineral is calcite. 



Geographical Distribution. The cobaltiferous arsenopyrites 

 are widely scattered along the Appalachian belt. Analyses of 

 this variety, called danaite, from Franconia, N. H., gave 6.45 

 per cent, cobalt. The scattered occurrences of nickeliferous 

 minerals in the Cordilleran section bear cobalt. 



The most important cobalt deposits of America are found in 

 the Province of Ontario, Canada, near the boundary line of 

 Quebec and west of the northern end of Lake Temiskaming. 

 It was during the construction of the Temiskaming and Northern 

 Railroad that the deposits of cobalt and silver minerals at Cobalt 

 were discovered. This was followed by a similar discovery at 

 South Lorrain and another at Gowganda. These fields have 

 given to Ontario a position amongst the leading silver camps of 

 the world. 



The geological' section at Cobalt has as its base a series of 

 highly folded diabases, granite porphyries, etc., that are intruded 

 by granites. This series is Kewatin in age. This series of ter- 

 ranes is separated from the Lower Huronian conglomerates and 

 slates by an erosional unconformity. Above the Lower Huronian 

 rocks is a series of conglomerates, quartzites and arkoses of 

 Middle Huronian age. Post-Middle Huronian diabases appears 

 in sheets and sills. Above the diabases there occurs Niagara 

 limestones and glacial drift completing the geological section. 

 The ores occur in the conglomerates, the diabases and the underly- 

 ing Kewatin series, although the lower formations are not so 

 productive of silver and cobalt. 



According to W. G. Miller the ores were deposited by highly 

 heated impure waters circulating through the cracks and fissures 

 following the intrusion of the post-Middle Huronian diabase. 



