506 NEW YORK STATE MUSEUM 



minerals. Both localities are very extensively faulted; the face of 

 Skiff mountain shows a fault cliff, and at Hammondville fault 

 breccias are of frequent occurrence. 



Magnetite was found by the writer in the Desolate brook valley, 

 southwest of Pharaoh mountain. It had been tapped by a mine, 

 apparently long abandoned. The foot and hanging walls were of 

 the same type of granite as those of the former localities. 



These deposits are in striking contrast to the titaniferous ore 

 bodies, the magnetites showing no intimate relation to the wall rock. 

 The conclusion seems inevitable that they are foreign tO' the granite, 

 and produced in connection with one of the later intrusions, prob- 

 ably secondarily enriched by percolating water. Similar ores near 

 Port Henry^ have been described by Professor Kemp. There the 

 ores are associated with an igneous intrusion of gabbro ; they are 

 always within an acid gneiss, but their proximity to the gabbro ren- 

 ders their origin as contact occurrences the most reasonable view. 



The Hammondville and Schofield ore bodies are cut off by faults 

 from all neighboring intrusions, but their most probable relationship 

 seems to be with intrusive action. 



The alternative hypotheses would be either to regard the mag- 

 netite as a metamorphosed sedimentary bed and the Hammondville 

 gneiss as a sedimicnt, which is improbable in view of its similarity 

 to the Pharaoh granite ; or else to consider it a magmatic segregation 

 from the granite, which seems improbable in so acidic a rock, notably 

 poor in iron. 



^ J. F. Kemp. Geology of the Magnetites near Port Henry N. Y. and 

 especially those of Mineville. Trans. Am. Inst. Min. Eng. 1897. 



