84 NEW YORK STATE MUSEUM 



as nodular particles surrounded by the sulphides, and are of the 

 same nature as the silicate inclusions in the limestones. It is rather 

 evident that they were formed before the ore, representing the 

 unreplaced matter in the process of mineralization. 



In the second type the sulphides are disseminated through the 

 limestone, usually within a more or less restricted zone which itself 

 constitutes a band or lens that on the borders shades off into the 

 country limestones. The percentage of sulphides is much smaller 

 than in the other type, in most examples constituting but a small 

 per cent of the whole mass. The individual grains of pyrite and 

 blende are surrounded by those of dolomite; and silicate minerals 

 abound, often constituting nodular bodies that measure several 

 inches to a foot in diameter. The size of the metallic particles 

 averages much smaller than it does in the richer ores illustrated by 

 the first type. 



As to the general distribution of the ores in the limestone it can 

 be said that they favor the border zone more often, than otherwise. 

 Although some showings have been found within the middle of the 

 belt, they are mainly of the disseminated form of occurrence which 

 has not yet been proved to be of commercial value. 



It is also noticeable that the limestone in the vicinity of the 

 deposits is always impure, owing to the presence of silicates. In 

 their original form these consisted of tremolite and diopside but 

 they are now mostly altered to serpentine and talc. The association 

 of the ores with the silicated layers is too constant to be merely 

 accidental, but points to a genetic relationship which need not be 

 explained, however, in this place. The vicinity of the talc mines 

 offers favorable ground for prospecting for zinc. The fact that 

 the sulphides have not been penetrated in the mines themselves is 

 to be explained by the fact that the openings are carried always 

 within the talc, never reaching out into the country rock in the 

 ordinary course of operations. The writer discovered some good 

 specimens of zinc blende in the dump of one of the mines in which 

 exploratory work for the purpose of finding a possible continuation 

 of the talc had been carried into the overlying limestone. 



Another suggestion for the guidance of prospecting operations is 

 prompted by the occurrence of the hematite deposits which at one 

 time were actively worked for the supply of the Fullerville furnace. 

 The hematite, not unlikely, may prove to be the gossan or oxidized 

 outcrop of the sulphides, as was suggested by the writer in nn 



