RE-EXAMINATION OF AMERICAN MINERALS. 141 



It will be seen that this forms no exception, and when 

 examined pure has the same composition as spodumene from 

 other localities. In fact, so far as the American spodumene is 

 concerned, we believe that the specimens from Norwich are the 

 most beautiful that have been found any where, and we shall 

 take pleasure on some early occasion in furnishing Eammels- 

 berg with good specimens from both Norwich and Sterling. 



36. Petalite. 



In connection with the analyses of spodumene it was thought 

 interesting to examine the American petalite. For this purpose 

 a specimen from Bolton, Massachusetts, was selected. The re- 

 sults of analyses are : 



.771 

 .18) 



1 Oxygen. 



Silica 77.95 40.50 



Alumina 16.63 7.77 



Peroxide of iron ... .62 



Lime trace 



Magnesia 21 .08 



Lithia 3.74 2.07 



Soda . 48 .12 



Potasa trace 



Ignition .60 



100.23 



'No. 1 gives oxygen ratio 20 : 3.92 : 

 ratio 20 : 3.74 : 1.08, or quite nearly 

 have the formula R 3 si4_|_43tl Si*= silica 78.37, alumina 17.44, 

 lithia 3.40, soda 0.79. 





2 Oxygen. 





77.90 40.47 



7.95 



15.85 7.411 7*« 

 .51 .15/ '- 56 





trace 





.26 .10 1 



2.27 



3.52 1.94 L 2.18 





.53 .14 J 





trace 





.70 





99.37 



1.12; 



No. 2 gives oxygen 



20:4 



: : 1, from which we 



37. BOLTONITE, IDENTICAL WITH CHRYSOLITE. 



Boltonite was first described as a new species by Professor 

 C. TJ. Shepard. He made the specific gravity from 2.8 to 2.9. 

 It was subsequently examined by Professor Silliman, jr., who 

 found 3.008 as its specific gravity, with a hardness of from 5 to 6. 

 His analysis gave for its constituents 



Silica 46.062 



Alumina 5.667 



Magnesia 38.149 



Protoxide of iron 8.632 



Lime 1.516 



With this knowledge of the mineral I undertook its exam- 

 ination on specimens in the gangue furnished me by Professor 

 Shepard. Examination of different portions separated mechan- 



