III. — The Monoclinic Pyroxenes of New York State. 



BY HEINRICH RIES. 



Read March 17th, 1895. 



Contents. 



Introduction 124 



Literature 125 



General Characters of Pyroxene 12S 



Distribution of the New York Pyroxenes '. 131 



Characters of the New York Pyroxenes:— 



Crystallography 133 



Optical Properties 137 



Etch-Figures 140 



Alteration Products 142 



Detailed Account of Occurrences: — 



Augite 144 



Leucaugite 163^ 



Hedenbergite 165 



Sahlite 167 



Diopside 16& 



Genesis of the New York Pyroxenes 175 



Introduction. 



The following paper is intended to give the results of a orys- 

 tallographic, chemical and optical investigation of the mono- 

 clinic * pyroxenes occurring within New York State, and to this 

 is added such information as has already been published by others. 



In the course of this work the pyroxenes in the collections of 

 the following institutions have been examined : School of Mines, 

 Columbia University ; American Museum of Natural History, 

 New York City ; The New York State Museum, Albany, N. Y. ; 

 Rutgers College, New Brunswick, N. J. ; National Museum, 

 Washington, D. C. ; Hamilton College, Clinton, N. Y. ; Cornell 

 University, Ithaca, N. Y. ; Williams College, Williamstown, Mass. • 

 as well as the private collections of Prof. Thos. Egleston, Prof» 

 A. H. Chester and Mr. F. L. Nason. 



* This does not include wollastonite. 



