Constituents of various Minerals. 265 



Strontian, where it is one of the various substances which serve 

 as a gangue to the ore. 



The colour is snow-white. 



The mineral is massive. Structure foliated, or at least scaly. 

 Fracture even. 



Rather softer than common sulphate of barytes. Indeed it 

 is scratched by the nail. 



Sectile. 



Lustre pearly. 



Translucent on the edges. 



Specific gravity 4.1907. 



It was analysed by Mr THOMAS MUIR, who found the con- 

 stituents as follows : 



Sulphuric Acid, . . . 34.540 



Barytes, 48.945 



Lime, 6.605 



Silica, 4.140 



Alumina, 3.460 



Protoxide of Iron, . . 0.450 



Strontian, 0.790 



Carbonic Acid, . . . 0.334 



Moisture, 0.565 



99.829 



The mode of analysis followed was to heat the pounded mi- 

 neral with carbonate of soda, till complete decomposition was in- 

 duced. The heated mass was softened in water, and digested in 

 that liquid till every thing soluble was taken up. The alkaline 

 liquid was saturated with muriatic acid, and evaporated to dry- 

 ness to obtain the silica. The dry mass was digested in water, 

 acidulated with muriatic acid. The silica left behind was edul- 

 corated, ignited, and weighed. The muriatic acid solution was 

 mixed with a sufficient quantity of muriate of barytes to throw 



