146 RE-EXAMINATION OE AMERICAN MINERALS. 



view was sustained by the apparently perfect accordance in 

 the physical characters of the two minerals, coupled with 

 the fact that the amount of silica and water in the two, as 

 already examined, was the same, and also the sum of the 

 oxides of iron and alumina in the owenite were equal to the 

 sum of the oxides of iron in the thuringite. To settle the 

 question, it became necessary to re-examine thuringite, of 

 which I obtained a specimen from Mr. Markoe, coming from 

 the original locality; it was slightly altered by the action of the 

 air, but this could interfere only with the correct estimate of the 

 protoxide of iron. Its specific gravity was 3.186, and its com- 

 position 



Silica 22.05 



Peroxide of iron 17.66 



Alumina 16.40 



Protoxide of iron 30.78 



Magnesia 89 



Soda ") 1 . 



Potash / 14 



Water 11.44 



99.36 

 The peroxide of iron is a little higher and the protoxide 

 a little lower than in the analysis of owenite, but this arose 

 from the partial decomposition of the specimen. The correct 

 analysis of thuringite is that first given, and the formula de- 

 duced by Mr. G-enth from it is to be looked upon as the correct 

 one — namely, 2R 3 Si+K 3 Si+6H, corresponding to the oxygen 

 ratio for S, U, Si, H, 1 : 1.5 : 1.5 : 1. 



In looking over some minerals placed in my hands by Mr. 

 Markoe, I have found a specimen of thuringite coming from 

 the Hot Springs of Arkansas. Its identity is made out without 

 the slightest difficulty, as all its physical characters correspond 

 most perfectly with the thuringite, its specific gravity being 

 3.184 and composition 



Silica 23.70 



Peroxide of iron 12.13 



Alumina 16.54 



Protoxide of iron 33.14 



Magnesia 1.85 



Manganese 1.16 



h } 32 



Soda 

 Potas 

 Water 10.90 



99.74 



