146 The Moyioclinic Pyroxenes of Neiv York State. 



which passes into the normal limestone. The pyroxene in the 

 limestone at the contact often shows well developed crystals. 

 Graphite is common in the limestone. 



The augite crystals from Diana are generally black or greenish 

 black, and in section green. They have smooth, but dull faces. 

 Doubly terminated specimens are not rare, and a basal parting is 

 nearly always present. The oi'dinary combination of forms is 

 a(lOO), 6(010), m(110),M(llI), s(Tll), oC"221) and z(021), (PI. 

 XYI.,Fig. 6). Other combinations observed on crystals from this 

 locality in the Columbia University, School of Mines collection 

 arem(110),6(010),c(001),M(lll),"o(l21) and s (111); a (100), 

 and b TOIO) broad, m (110) narrow, c (001) broad, e (Oil) narrow, 

 and u (111) small, (PI. XYI., Fig. 1). The latter resembles the 

 common Orange County form. A strong prismatic cleavage is 

 sometimes present, and the crystals often reach a large size one 

 in the School of Mines collection being five inches long, three inches 

 thick, and with the forms a (100), 6 (010), m(llO), c(001),and 

 ( 221). It closely resembles the dark green augite from Russel. 



The following combinations of forms from Diana are noted by 

 L._C. Beck (Ref. 2) m(llO), o (^^1), ^; (221) ; a (100), m (110), 

 0(221); a(lOO), 6(^10), m(llO), 0(^21); a (100), 6 (010), m (110), 

 e(OOl), i6(lll), s(lll); and a(lOO), 7?r(110), e (Oil), v (221). 



There is in the Root collection at Hamilton College, a light 

 green crystal from Diana which has the forms a (100). & (010), 

 m (110), p (TOI), (221), and A ("331). (PL XY., Fig. 8). The 

 crystal is twinned many times parallel to c (Oil), and once par- 

 allel to a (100), the twinning plane dividing it sj^mmetrically. 

 The similarity of this twin to those of fassaite from Monzoni in 

 the Tyrol has been pointed out by G. v. Rath, (Ref. 41). 



An analysis of the common dark green pyroxene from Diana gave 



Per cent. Ratio. Prop, parts. 



SiO, 53.97 .8995 290 



FeO 8.63 .1198 39 



CaO 23.96 .4278 133 



MgO 7.32 .1830 60 



AlA 4.94 .0482 15 



FeA 0.50 .0031 1 



99.33 

 Sp. Gr. 3.36 



This gives Cai33Mg6o'Fe39Fe2Al3oSi29o084o 



