Minerals containing Columbium. 409 



The longitudinal faces of the prisms are quite smooth. 

 It is probable, from this crystal that the primary form of 

 torrelite is a right oblique prism terminated by a rhombic 

 bar, whose angles are 84° 20' and 95° 40'. The trianglar 

 face o is too rough on the surface for measurement. It is 

 sensibly an equilateral triangle, and its inclination to the 

 adjacent edge, is about 143° 45' from a mean of several 

 trials. 



The colour is black, or at least much darker than that 

 of columbite. The surface is iridescent, with a play of blue 

 and red colours. 



Lustre imperfectly metallic, almost resinous, being very 

 similar to that of cherry coal. In one direction (parallel 

 to face M) it is imperfectly foliated. Cross fracture gra- 

 nular. Opaque. " * 



Hardness 4-25. Specific gravity 4-8038. 



Before the blow-pipe both with carbonate of soda and 

 borax, it fuses into a dark red bead, shewing the presence 

 of iron. With a great excess of carbonate of soda, the 

 green colour characteristic of manganese makes its appear- 

 ance. When reduced to a fine powder the colour is dark 

 chocolate brown. 



1. 100 grains being exposed to a red heat, lost 0*35 

 grains of weight, which was considered as water. 



2. 20 grains of the mineral in fine powder were mixed 

 with 160 grains of crystallized bi-sulphate of potash, and 

 gradually heated in a platinum crucible, over an Argand's 

 spirit lamp. Care was taken to keep the heat moderate 

 till the ebullition of the salt was at an end. It was then 

 raised to redness, and the whole was kept in fusion for, at 

 least, a quarter of an hour. 



3. The red mass on cooling became white with an ex- 

 ceedingly slight tint of slate blue. It was softened in 

 water and finally digested in muriatic acid for 24 hours. 

 The whole was then thrown on a filter, and the white 

 powder collected on the filter was thoroughly washed with 

 boiling hot water. It was then dried in the open air, and 

 digested for 24 hours in a solution of caustic ammonia. 



4. The ammoniacal solution was then filtered off, and 

 saturated with muriatic acid. A white flocky precipitate 

 fell, which, after ignition, assumed a shade of brown, and 

 weighed 009 grain. 



