180 Bradley — Composition of the Mineral Warwickite. 



of American minerals, pointed out that warwickite possessed 

 a peculiar composition altogether different from what had 

 been supposed, and that the pure mineral had not yet been 

 analyzed. When the mineral had been subjected by the 

 gentlemen named to a careful qualitative analysis, it was 

 found to their great surprise to contain a large amount of boric 

 acid, hitherto overlooked, so that it was to be considered as a 

 boro-titanate of magnesia and iron. The quantitative analysis 

 undertaken by Smith was made with difficulty because of the 

 small amount of material available and from the fact that 

 minute crystals of spinel penetrated those of warwickite. 

 Smith, however, was finally satisfied that the results obtained 

 expressed the true composition. The specific gravity obtained 

 (Brush) was 3*362, and Smith's analysis is as follows : 



Oxygen Eatio 



B 2 3 _-___ 27-80 19-06 9 



Ti0 2 23-82 10-37 5 



MgO 36-80 14-46 6 



FeO 7'02 2-10 1 



Si0 2 1-00 



A1 2 G 3 ____ 2-21 



98-65 



Smith regarded , the silica and alumina as impurities, the 

 latter arising from the spinel that it had been impossible to 

 separate ; this, with a little of the magnesia, he deducted in 

 making out the oxygen ratio from which he derived the 

 formula : 



6MgO . lFeO . 2Ti0 2 . 3B 2 3 . 



Method of Analysis. — The material used for the present 

 analysis was obtained from the Brush collection and came from 

 Amity, N. Y., where this mineral is found as a characteristic 

 associate of the granite contacts of the region. The warwick- 

 ite occurs in minute slender crystals showing the copper-red 

 reflections of the cleavage surfaces which is so characteris- 

 tic of the pure mineral. It is found in a coarsely crystalline 

 white limestone, intimately associated with a greenish blue 

 spinel, black spinel, magnetite, serpentine, chondrodite and 

 occasional scales of graphite. The limestone rock containing 

 the minute crystals of warwickite was crushed to small frag- 

 ments and these small pieces, which contained some of the 

 mineral, were carefully selected by means of a glass. This 

 material was again crushed and prepared for treatment with 

 heavy solutions. Potassium mercuric iodide solution, having 

 when concentrated a specific gravity of 3*15, was first used to 

 separate the greater part of the calcite and serpentine. The 



