104 NEW YORK STATE MUSEUM 



between the talc and the dolomitic limestone. Veinlets and threads 

 of the same type of serpentine are found intersecting the sulphide 

 bodies, the mineral here having been deposited from solution sub- 

 sequent to the introduction of the ores. 



Vein quartz is much in evidence around the ore bodies, specially 

 those at Edwards; at this locality a band of white quartz 10 feet 

 thick is exposed near the southern workings with a strike parallel 

 to that of the ore bodies. There are numerous smaller stringers 

 that intersect the limestone in all directions. Inclusions of talc 

 were found in the quartz and it apparently represents a relatively 

 late period of deposition. 



The general association of the sulphides and accompanying min- 

 erals seems to bear evidence of the work of underground waters, 

 which in an extended period of circulation through the limestones 

 have introduced and deposited various ingredients. To the earliest 

 stage of their activity is perhaps to be assigned the partial dolomiti- 

 zation and silication of the limestones which resulted in the forma- 

 tion of talc. It is recognized that the latter may have been derived 

 from tremolite as is the case of most of the talc in the near-by talc 

 district, but tremolite itself is a secondary mineral that was found 

 either as the result of metamorphism of impure siliceous seams 

 within the calcareous sediments or else from the reaction of silica- 

 bearing solutions upon the limestones after their deposition and 

 uplift. Without going into details of evidence, it may be said the 

 latter view seems rather more probable. The underground waters 

 next brought in iron and zinc, depositing them as sulphides in molec- 

 ular interchange with the limestone. Following this, the lime- 

 stones were subjected to compression which resulted in a brecciated 

 condition, together with a certain amount of flowage, as shown in 

 the Edwards exposures. The occurrence of quartz and serpentine 

 stringers is to be assigned to a later period of deposition subsequent 

 to that of the sulphides. 



The compact nature of the ores, their fine granular condition 

 and the general absence of characteristic vein types or structures, 

 all suggest that they were deposited in their present place when the 

 limestones were at considerable depth under cover of a heavy over- 

 burden. These conditions were undoubtedly present when the 

 limestones underwent metamorphism and recrystallization, but that 

 change seems to have been accomplished mostly previous to the 

 formation of the ore bodies. 



