154 NEW YORK STATE MUSEUM 



analogous to the mica gneiss above the upper ore at Stella, but the 

 rocks at the two localities are quite unlike, while at none of the 

 previously described localities is there anything resembling the dark, 

 hornblende gneiss in the present section. The ore deposits them- 

 selves and the immediately associated rock appear without doubt to 

 be of the same general type as elsewhere. 



While in the preceding cases it has been clear that all rocks con- 

 cerned, with the exception of the pegmatites, were of the generally 

 accepted Grenville sedimentary types, at Stella this is far from being 

 the case, and for the first time the question of the origin of extensive 

 rock bodies presents itself. 



The problem begins with the dark, hornblendic gneiss at the bot- 

 tom of the section. This is a type of rock that might result from 

 the metamorphism of a sediment or of a basic igneous rock. In the 

 present case conclusive evidence is not afforded for deciding between 

 the alternatives, but from a general knowledge of the region, and 

 more particularly from evidence to be given in connection with 

 another locality, the writer inclines to regard the rock as igneous and 

 closely related to the gabbros of the region. Yet this view meets 

 difficulties when the gneiss between the ore bodies is examined. The 

 central part of this can hardly be distinguished from the supposed 

 gabbro, but it shades both upward and downward into a light gray, 

 rather acid gneiss that might well be interpreted as a Grenville sedi- 

 ment. Evidently this difficulty might be explained in diverse ? 

 vv^ays, but without very detailed study speculation would be • 

 fruitless. Finally, the mica gneiss above the upper ore is regarded 

 as probably sedimentary, but on the other hand it too may be a meta- 

 morphosed intrusive so far as can be judged by its structure and 

 mineralogical composition. 



While these unsettled questions obviously are important in their 

 bearing upon the history of the ore deposits, they are not so vital as 

 they would be were this the only locality for the pyrite or did the 

 deposits here differ markedly from those at the other localities. As 

 a matter of fact, this latter is conspicuously not the case, the ore 

 bodies at Stella agreeing in all important details with those already 

 described. This being true, it follows that the nature of the ore | 

 deposits is independent of the immediate presence of large intrusive 

 masses, since none occur at the other localities, and the probable and 

 possible intrusions at Stella have exerted no noticeable modifying 

 influence upon the ore bodies. The latter are of rough lens shape, 



