The Monoclinic Pyroxenes of New York State. 14T 



or 39 (CaFeSiaOe) 

 IsJAl^SigOg) 

 60 (CaMgSi^Oe) 



CaFejSiOs 

 SSCCaSiOa) 



leaving 81^202 6' which is approximately SiOj. 



c : £ 41° 30^ 



a 1.6888 



y3 1.6932 



7 1.7108 

 Y—a .022 



2W* 79° 27^ 



2V 60° 40' 



Gouverneur, St. Lawrence Go. — Bright gray and dark green 

 pyroxene occurs associated with hornblende in the limestone one 

 mile southeast of Gouverneur (Ref. 2, p. 295). A flat crystal 

 tabular parallel to 6(010) is figured by Prof. S. L. Penfield in 

 Dana's System of Mineralogy, 1893. The forms on it are a (100), 

 &(010), m(llO), c(001),m(111),'u(221) and A ("311). 



Augite in rounded masses and with an extinction angle of 40°^ 

 occurs in the schist underlying the limestones at Gouverneur. 

 In the gneisses the pyroxene in section is pale and colorless and 

 has an extinction of 45°. It shows a certain amount of alteration 

 to chlorite, but changes mostly to uralite. Pyroxenic phases of 

 the limestone are nob uncommon, the latter containing colorless 

 grains of pyroxene with a high extinction angle (Ref. 48). 



The dark green crystals which the writer has seen from this 

 locality are usually of prismatic habit and without terminations. 

 One form in the Collection of the School of Mines, Columbia 

 Universit}^ shows a (100), 6(010), c(OOl), with 'w(lll), and 

 s( 111), very small (PI. XIV., Fig. 4). A white and much decom- 

 posed crystal in the same collection has the planes a (100), 

 6(010), m (110), c (001), and w(lll). (PL XVI., Fig 4). 



HaTnmondville, Essex Go. — There is a small black crystal with 

 smooth dull faces from this locality in the collection of Cornell 

 University. (PI. XIV., Fig. 1). The planes noted on it are 

 m(llO), and 6(010) broad, a (100) narrow, and the terminal faces 

 are c(OOl), and s( 111). The crystal is a very well formed one 

 considering its occurrence with magnetite. The sp. gr. is 3.5. 



Black pyroxene associated with magnetite occurs on the shore 



*2W=inH,0. 



