The Monoclinic Pyroxenes of New York State. 167 



From Vanuxem's analysis this mineral would be classed as an 

 augite, but the high percentage of ferrous iron in the analyses of 

 Smith and Brush tend to class it with hedenbergite. It does 

 not agree with the theoretical composition of hedenbergite in that 

 it contains too small a percentage of lime, and is, therefore, 

 as stated above, intermediate between augite and hedenbergite. 



There is a small specimen of this mineral in the Columbia Uni- 

 versity collection and another fine specimen in the collection ol 

 the New York State Museum at Albany. 



Sahlite. 

 Willsborough., Essex Co. — A granular green pyroxene associ- 

 ated with granular garnet and wollastonite occurs in a vein at 

 this locality (Ref. 2, p. 289). The grains are nearl}^ transparent 

 and the material has a semivitreous lustre. An analysis b}^ 

 Seybert gave : 



Percentage. Ratio. Prop, parts. 



SiO., 50.33 .839 60 



FeO 20.40 .283 20 



CaO 19.33 .345 25 



MgO 6.83 .170 13 



AlA 1.53 .914 1 



HjO 66 



MnO ■■ tr 



99.08 

 Sp. Gr. 3, Sn. 



The above analj^sis corresponds to the formula Mgg Fcoq Caag 

 All SigoOi^g, which is intermediate in composition between 

 sahlite and hedenbergite, but nearer to the former. 



An analysis of pyroxene from Edenville, analyzed by G. W. 

 Hawes (Ref. 19), was published, together with one of hornblende 

 from the same locality, as proofs that " when parallel growths of 

 two minerals occur, which under different conditions can be made 

 to crystallize from the same material, chemical composition deter- 

 mines the difference." 



Percentage. Katie. Prop, parts. 



SiO^ 51.05 .85 100. 



AlA 2.02 .019 2 



FeO .....12.18 .169 20 



CaO 22.07 .394 47 



MgO 10.02 .250 30 



FeA 1.36 .0085 1 



MnO 12 .016 2 



H^O .34 



99.10 



