The Monoclinic Pyroxenes of Neio York State. Ill 



ning and the accompanying parting are common. The general 

 combination of forms is a (100), &(010), m(llO) and c'(001.) 

 Another form figured by Prof. Penfield in Dana's System of Min- 

 eralogy, 1893 shows a(lOO), &(010), c(OOl), it(lll),'i;(221) and 

 p(101.) Parallel growths of pyroxene with hornblende are fre- 

 quent. (Ref. 38) and G. Y. Rath has described crystals from 

 Pierrepont, whose prism faces were covered with numerous small 

 individuals. (Ref. 38.) The extinction angle of the Pierrepont 

 diopsides is 37°. 



Pitcairn, St. Lawrence Go. — An unusual form from this locality, 

 and belonging probably with the diopsides, is a small group of 

 crystals in the collection of Cornell University. The crystals 

 are ^^ an inch long, with bright faces. They are of very simple 

 form showing only the planes m (110), u (111) and s (111), (PL I, 

 Fig. 8). 



Port Henry ^Essex Co. — The occurrence of white pyroxene as an 

 unaltered core of the serpentine grains and masses in the ophical- 

 cites of the eastern Adirondacks has long been known, but so far 

 as the writer is aware the occurrence of white pyroxene crystals 

 fi'ee from serpentine is uncommon. During the summer of 1893, 

 Prof. Kemp found a great quantity of this interesting variety in 

 a limestone quarry north of Port Henry, where it occurs together 

 with yellow titanite, hairbrown amphibole and graphite. The 

 amphibole is idiomorphic with respect to the pyroxene and tit- 

 anite. Scales of graphite surround the pyroxene and penetrate 

 it, and shots of the same mineral often appear on the faces in the 

 prismatic zone, but none were noticed on the terminal faces, 

 neither were there any on the amphibole or titanite. 



The diopside individuals though usuall^^ white are sometimes 

 pink. The^'^ are translucent, and vary in length from one-tenth 

 to half an inch, with smooth bright faces. A strong basal part- 

 ing is not uncommon, but is wanting in the perfectly fresh and 

 transparent individuals. An orthopinacoidal parting is occasion- 

 ally met with. 



The general combinations of forms occur, viz., a (100), &(010), 

 m(llO), c(OOl), 16 (111), s (111) and p (lOl). (PI. II, Fig. 10), 

 and a (100), 6(010), m (110), c (001), e (Oil) and p (101). (PL, 

 II, Fig. 9). The pyramids and clinodomes rarely occur on the 

 same crystal. One specimen in the private collection of Prof. 

 Kemp has the face o (221). 



