286 Dr. Thomas Thomson [April 



splendent, resinous, the faces of the crystals are frequently 

 rough and have little lustre ; easily frangible ; hardness 4*5 ; 

 specific gravity 4*551. 



Before the blowpipe assumes a red colour but does not 

 fuse, on cooling it resumes its natural colour and appear- 

 ance. When heated on charcoal it becomes darker but 

 does not melt. With carbonate of soda it does not fuse ; 

 but the soda while in fusion appears red, on cooling it re- 

 sumes its white colour. With biphosphate of soda it does 

 not fuse. The flux while in fusion assumes a fine red 

 colour ; when it becomes solid, the colour changes to yel- 

 low ; and when quite cold, it resumes its usual colours and 

 transparency, the assay remaining unaltered in the centre. 

 With borax it dissolves very slowly. The bead is trans- 

 parent and has a very deep garnet red colour. 



1. To determine the component parts of this mineral, 

 100 grains of it were reduced to a very fine powder, and 

 heated for an hour in a platinum crucible with thrice the 

 weight of anhydrous carbonate of soda. The mixture 

 had been fused, and when cold had a fine green colour, 

 indicating the presence of manganese in the mineral. On 

 digesting the fused mass in muriatic acid, 67 grains of the 

 mineral remained undecomposed. 



This residue was again fused with thrice its weight of 

 carbonate of soda, and kept for an hour in a strong red 

 heat ; the fused mass was similar to the former. Being 

 digested in muriatic acid, 33 grains of the mineral still 

 remained undecomposed. 



These 33 grains being treated with thrice their weight 

 of carbonate of soda as before, the whole dissolved in mu- 

 riatic acid, except a few flocks; which being heated a 

 fourth time with carbonate of soda, and the mixture di- 

 gested in muriatic acid, a complete solution was obtained. 



2. The solution in muriatic acid had a strong yellowish 

 red colour, shewing that the mineral contained much per- 

 oxide of iron. They were all mixed together and evapo- 

 rated to dryness in a porcelain dish. 



3. The dry mass, which had a yellow colour, was digested 

 for an hour in water, acidulated with muriatic acid, and 

 then passed through a filter. There remained on the filter 

 a white powder, which, being washed, dried and ignited, 



