The Monoclinic Pyroxenes of New York State. 133 



Other isolated pyroxene occurrences are at the Tilly Foster 

 Mines, Putnam Co., and at New Kochelle, Westchester Co., the 

 former associated with magnetite in gneiss and the latter with 

 serpentine. 



Pyroxene is very abundant at certain localities in the dolomitic 

 limestones of Dutchess, Putnam, Westchester and New York 

 Counties. The crystals all bear the closest resemblance to one 

 another, and are found singly, in streaks, or in clusters lining 

 oavities. A massive form of the same species occurs at times. 

 The important localities are Kingsbridge, New York Co., Sing 

 Sing, Westchester Co., Pawling and Paterson, Dutchess Co. 

 The dolomites in which these pyroxenes occur have been highly 

 metamorphosed by dynamic action. 



It will be seen from the foregoing that the pyroxenes occur in 

 New York State under the following conditions : 1. As primary 

 constituents of igneous rocks. 2. In the contact zones between 

 the limestones and intrusive rocks. 3. In crystalline limestones 

 in areas of regional metamorphism. 4, Associated with the iron 

 ore bodies. 



In general, it may be said that the lighter colored varieties 

 occur in the limestone, while the darker ones are found along the 

 contact zones and in the igneous rocks. The minerals usually 

 found associated with the pj'^roxene are scapolite, feldspar, wol- 

 lastonite, amphibole, titanite, mica, tourmaline, garnet, chond- 

 rodite, zircon and quartz. The pja'oxene occurs both massive or 

 in crystals that are scattered through the rocks or that form clus- 

 ters lining veins or cavities. These latter are generally filled in 

 with calcite or quartz. 



General Characters or the New York Pyroxenes. 

 Crystallography. 

 The forms occurring are comparatively few in number, but the 

 •combinations and their relative development of faces are, inmost 

 instances, quite characteristic of the locality. These peculiarities 

 are mentioned under the detailed descriptions of the different 

 localities. The great majority of the specimens found only show 

 faces in the prismatic zone, owing to adverse conditions of 

 growth. Doubl}^ terminated individuals are not uncommon but 

 they have not been observed from every localit3\ 



Annals N. Y. Acad. Sci., IX, May, 1896.— 10. 



