158 . NEW YORK STATE MUSEUM 



Fowler and Edwards, The limestone belongs to the same series 

 that yields the Gouverneur marble and may be classed as Algonkian. 

 In the section under consideration the limestone is characterized by 

 the abundant presence of silicates, which oftentimes constitute the 

 greater part of the rock mass. The talc mines of St Lawrence 

 Q^ounty all lie within this limestone belt, the mine first opened being 

 within a short distance of the zinc mine. 



The ore is zinc blende, containing some galena and usually con- 

 siderable pyrite. So far as prospecting operations have gone its 

 occurrence seems to be limited to the limestone near the contact 

 with the gneiss. The gangue is a mixture of calcite and serpentine, 

 the latter being evidently an alteration product, probably of horn- 

 blende or pyroxene. The presence of ore is indicated at the surface 

 by rusty, disintegrated material or gossan, due to the oxidation of 

 the pyrite. There is usually only a slight depth of this material, and 

 unaltered zinc blende may be found within a foot or less below the 

 thin soil capping. 



The main discoveries are located along a low ridge immediately 

 north of the Oswegatchie river. Near the north end an open cut 

 has been made into the ridge, affording a good exposure of the 

 limestone. The strata have a northeasterly strike and a variable 

 dip to the northwest. At this point the ore seems to occur in 

 irregular bunches aggregated along a band in the limestone. The 

 width of the band of mixed ore and rock is about 15 feet in its 

 maximum development. Masses of ore are also found included in 

 the limestone at some distance from the main body, and the general 

 appearance at this locality is suggestive of a brecciated and possibly 

 faulted deposit. 



Several openings have been made south of the one mentioned for 

 a distance of 2000 feet, all showing some ore. At a point about 

 1000 feet south, a rich band, 5 or 6 feet thick, has been uncovered 

 and followed to a depth of 15 feet. This body lies considerably to 

 the east of the general trend of the principal ore belt, but whether 

 it represents a displaced portion of the latter could not be determined. 



The bulk of the ore has a granular texture, with the metallic 

 minerals distributed somewhat regularly through the limestone 

 matrix. The blende shows little or no tendency to crystal form, 

 but the pyrite quite often exhibits a cubical development. The 

 proportion of the latter mineral varies widely, being absent in some 

 specimens and again very abundant. As to the zinc content it is 

 stated that an average sample of the richest ore gave 48%, while 

 the lowest assay showed 13%. About 3000 tons of ore have been 



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