282 ' NEW YORK STATE MUSEUM 



The pyrite, associated with more or less pyrrhotite, occurs in cer- 

 tain weU-defined belts of Grenville gneiss, of which the more im- 

 portant have been recently mapped by A. F. Buddington for the 

 State Geological Survey. There are at least 9 or 10 individual 

 belts, so far known, distributed over the region, but those of most 

 interest from a mining standpoint are grouped within a single zone 

 that stretches from the town of Canton in the central part of St 

 Lawrence county southwest for some 40 miles to and beyond Ant- 

 werp in Jefferson county. The developed deposits all lie in this 

 zone ; they include the Pyrites and Stella mines near the north- 

 eastern extremity, both with abundant resources, the Cole mine 

 opened in a large ore body near the center, and several others which 

 are to be classed as prospects so far as exploration is concerned, 

 but with the appearance of substantial deposits. 



All the deposits possess a certain similarity in their physical sur- 

 roundings and mineral character, however much they may differ 

 in the details of form, size or content. They are associated with 

 one of the characteristic Grenville rocks (a banded rusty gneiss) 

 which varies in individual layers or beds from a quartz- feldspar- 

 biotite gneiss to nearly pure quartzite and not infrequently con- 

 tains intercalations of crystalline limestone. The rock occurs in 

 belts that extend northeast and southwest, usually for distances 

 of several miles, but of narrow width. Careful study of the field 

 features has revealed that these belts are parts of a single series 

 of beds repeated by folding, the strata having been tightly com- 

 pressed and overturned so as to give a common inclination to all, 

 the dip being almost invariably northwest and usually at a high 

 angle. In outcrop the gneiss is distinguished by its rusty burnt 

 look which shows the presence of sulphides, and where concealed 

 its occurrence is denoted by the red color imparted to the soil. 

 The gneiss with its disseminated pyrite is much like the " fahl- 

 bands " that are described in connection with metalliferous veins in 

 the crystalline schists, whereas the concentrated pyrite that consti- 

 tutes the deposits proper may be likened to the veins themselves. 



The .workable bodies partake of the tabular form of the gneiss, to 

 the structure of which they conform very closely. Their parallelism 

 with the foliation of the gneiss, the general similarity between the 

 ore and wall rock so far as qualitative mineral composition is con- 

 cerned, and the indefinite contacts seem at variance with the idea 

 of a secondary derivation for the sulphides but rather argue for 

 their primitive accumulation with the sedimentary wall rocks. On 



