166 I'he Monoclinic Pyroxenes of New York State. 



Percentage. Ratio. Prop, parts. 



SiO, 51.00 .850 25 



CaO 21.00 .375 11 



MgO 11.50 .287 9 



Fe.,0., 11.53 .072 2 



AlA 3.50 .034 1 



H2O 1.00 



99.53 



Sp. Gr. 3.5, Beck. 



3.43-3.46, Brewer. 



This analysis gives the formula CajiMg9re4Al2Si2g075 which 

 does not appear to be a simple mixture of isomorphous silicates, 

 but to consist of 9 (CaMgSi20g)+2 Fe203+Al2Si309, leaving 

 Ca2Si309 or approximately 3(CaSi03). From the above for- 

 mula deduced from Yanuxem's analysis the hudsonite could not 

 be classed with hedenbergite, but the two analyses of Smith and 

 Brush given below, place it intermediate between hedenbergite 

 and augite. 



The analysis of Smith and Brush (Ref. 41), is as follows : 



SiO, 39.30 38.58 



AlA 9-78 11.05 



FeO .30.40 30.57 



CaO 10.39 10.32 



MgO 2.98 3.02 



MnO 67 .52 



K2O 2.48 4.16 



Na^O 1.66 



H2O 1.95 1.95 



99.61 100.17 



These analyses of Smith and Brush cannot be calculated out in 

 a satisfactory manner. They both, however, contain a consider- 

 able percentage of the hedenbergite molecule. 



Smith and Brush claimed that their analj^ses showed that the 

 Hudsonite was a variety of augite. Kengott, on the other hand, 

 thought that according to the analyses Hudsonite belonged to 

 the amphiboles. Both Dana and DesCloiseaux placed it among 

 the augites on account of the cleavage. Kengott notes (Ref. 27) 

 that Hudsonite has a cleavage parallel to the prism of 124°, but is 

 near hedenbergite in composition. Dana, in commenting on this, 

 states that none of the specimens which he has seen show such a 

 prism angle. 



