226 M. Rose on those Minerals which possess [March, 



Silica 57*40 containing oxygen 28*87 



Lime 23-10 6-48 



Magnesia 1 6-74 6*48 



Alumina 0*43 



Protoxide of iron 0-20 



97-87 



Pyroxene from Pargas gave Mr. N. Nordenskiold the follow- 

 ing composition : 



Silica 55-40 containing oxygen 27-7 



Lime 15*70 4-4 



Magnesia 22-57 9-3 



Oxide of manganese . . 0-43 



Alumina 2-83 



Oxide of iron 2-50 



99-43 



2. Pyroxenes with Lime and Protoxide of Iron as Bases. 

 Hedenbergit from Tunaberg, in Sadermanland.* 

 The colour is greenish-black ; it is semihard in a high degree. 

 It occurs among the masses thrown out from a mine which is 

 now deserted (Marmorsgufvan) not far from the cobalt mines at 

 Tunaberg, together with quartz, partly pure and large foliated ; 

 partly granular with magnetical iron ore. M. Rose's analysis 

 gave the following result : 



Silica. 49-01 containing oxygen 24*65 



Lime 20-87 5-86 



Protoxide of iron 26-08 5-93 



Magnesia and oxide of 



manganese 2-98 



98-94 



3. Pyroxenes with Lime, Magnesia, and Protoxide of Iron, as 

 Bases, together with more or less Protoxide of Manganese. 



In these varieties of the pyroxene, a constant proportion of the 

 bases is wanting ; and there is, therefore, a great variety in the 

 composition. Among all varieties of this series of pyroxenes, 

 there are not two which have their bases combined in the same 

 proportion; even pyroxenes from the same place vary in their com- 

 position : all, however, follow the law which M. Rose discovered ; 



* Hedenberg discovered this mineral, which he likewise first analysed. The re- 

 sult of his analysis is, however, very different from M. Rose's. Specimens which 

 were obtained from Prof. Berzelius's collection were first analysed, and afterwards such 

 as M. Rose brought with him from the place. Both analyses agreed completely in 

 their results. 



