46 NEW YORK STATE MU5EUM 



already brought about by previous or independent metamorphosing 

 agencies. 



That the tirst alternative is untenable is strongly indicated by the 

 fact that pyritous gneisses of relative richness, though of no eco- 

 nomic importance, are known, as in the cases earlier cited, in nor- 

 mal sedimentarv- sequence and not in immediate association with a 

 basic intrusive. As regards the second alternative, it may be noted 

 that the low-grade portions of the ore-bearing stratum are so simi- 

 lar in pyrite content and in general appearance to the interbedded 

 pyritous gneisses at other points on the sheet, that no special 

 influence on the part of the gabbro need be invoked to account for 

 their present character. Accordingly if any effects are traceable 

 directly to this intrusive, they are restricted to the reconcentration 

 of the sulphide ore to those workable deposits that have ser\-ed as 

 the basis of the former industry- to which the village of Pyrites owes 

 its name. 



It is precisely these questions as to whether the mineral is derived 

 directly from the magma, and as to the method of its reconcentra- 

 tion to workable deposit if merely original in the sedimentarv- 

 gneiss, which have received such adequate treatment at the hands of 

 Professor Sm\th in the paper already cited. The present writer is 

 of the opinion, based solely upon the held relations in this quad- 

 rangle, and not upon chemical and petrographic studies of an ex- 

 haustive comparative nature, that the pyrite of this formation is 

 primarily of sedimentary origin, and that the effects of the gabbro. 

 if indeed this can be admitted to have had any effects (see page 

 63), were confined to the reconcentration of the material already 

 present as a component of the gneiss. The writer, however, has 

 not studied the areal features of any of the other pyrite deposits 

 of this portion of the State, and clearly apprehends that if applied 

 to the other localities, this view might be incapable of substantia- 

 tion; and that upon further, more detailed study, the theor>- of 

 igneous origin for the High Falls pyrite may prove to be the only 

 tenable one. Xevertheless, judging entirely from tlie results of the 

 present investigation, it appears that the total composition of the 

 sedimentary' xenoliths has been ver\- little affected by the gabbroic 

 intrusion. 



In the south-central part of the triangular area of Pyrites gabbro 

 are three other, but smaller, inclusions of pyritous gneiss. The 

 relationships are ver\- imperfectly disclosed, but as nothing was 

 seen which appeared to discredit the general interpretation applied 

 to the larger xenolith in the Pyrites gorge, it is assumed that all 



