1*12 The Monoclinic Pyroxenes of New York State. 



An analysis of the fresh material gaA^e 



Percentage. Ratio. Prop, parts. 



SIO., 54.57 .9095 70 



FeO 1.80 .0250 2 



CaO 23.25 .4151 32 



MgO 17.78 .4432 35 



ALA 1-12 .0129 1 



KP 7 



Ign .38 



99.80 

 . Sp. Gr. 3.27. 



The above analysis corresponds to the formula Ca3 2Mg3gFe2- 

 AlSi7o02i2 which is practically that of diopside. The optical 

 constants are 



C:C 41° 

 . Na. 

 a 1.6683 

 /? 1.6730 

 y 1.6902 

 y-a .0219 

 2W:=73°2r 

 2 V = 56° 30' 



The white pyroxenes of this region are of interest as being the 

 source of much of the serpentine in the ophicalcites of Port 

 Henry, Essex Co., and Bolton, Thurman and Warrensburg in 

 Warren Co. 



This process of alternation has been studied and described in 

 detail by G. P. Merrill. (Ref. 34). The blotches of yellowish 

 and greenish serpentine, or serpentine and white pyroxene occur 

 in the ophicalcite near Port Henry from an inch to a foot or more 

 in diameter. In the quarrj^ of the Ophite Marble Co., the serpen- 

 tine with white pyroxene nuclei is said to be very common, and 

 all stages of alternation can be traced. The following is an. an- 

 alysis from Dr. Merrill's paper of the fresh pyroxene and the 

 serpentine crust. 



Pyroxene. Serpentine. 



SiOa 55.26 42.17 



AI2O3 22 .30 



Fe203 22 1.57 



FeO 57 .64 



CaO 24.48 



MgO 19.53 41.33 



MnO tr. 



H2O 13.72 



100.28 99.73 



