4 Mr. D. Forbes' s Researches on the 



Bismuthine.—As before mentioned, this mineral is found at 

 the San Baldomero mine, where it occurs both in the form of 

 scales incrusting the masses of native metallic bismuth, and by 

 itself in small compact masses having a very highly developed 

 foliated structure. It occasionally occurs in long and fine aci- 

 cular crystals, which sometimes have an iridescent lustre, and 

 frequently are so intermingled with slender needles of black tour- 

 maline as to present a very peculiar and at first glance puzzling 

 appearance. 



Frequently perfect single crystals of mispickel are found im- 

 bedded in the more compact variety. The largest specimens 

 found never exceeded half a pound in weight ; in no case were 

 defined crystals obtained, and. in only one case were the needles 

 or plates observed to have terminal faces. 



Two perfect cleavages, with occasionally a less distinct third 

 cleavage-plane, were present, and the faces of cleavage invariably 

 possessed a brilliant metallic lustre. 



Hardness was never found above 2, and sometimes appeared 

 rather less. 



Specific gravity of a pure very compact specimen was found 

 to be 7*16 at 60° Fahr. 



The chemical examination was conducted as follows :— The de- 

 termination of the sulphur was made by heating. 20*02 grs. of 

 the pure mineral in finest powder, with a mixture of 60 grs. pure 

 nitrate of potash along with 70 grs. pure carbonate of soda in a 

 silver crucible ; it glowed gently and became semifused, but did 

 not flow. The mass, on cooling, was digested with water and 

 thrown on to a filter to separate the oxide of bismuth, which was 

 well washed. The filtrate was then acidified with hydrochloric 

 acid and precipitated by the addition of a solution of chloride of 

 barium. The sulphate of barytes thus thrown down was col- 

 lected as usual, and weighed 28*46 grs., equal to 3*926 grs. sul- 

 phur, or 19*61 per cent, sulphur in the mineral. The bismuth 

 was now estimated by dissolving the oxide left upon the filter, as 

 above mentioned, in nitric acid, and precipitating the solution 

 with carbonate of ammonia in excess. The precipitate, well 

 washed and ignited, afforded 18*03 grs. oxide of bismuth, cor- 

 responding to 16*202 grs. metallic bismuth, or 80*93 per cent, 

 in the mineral. 



An equal amount of the original mineral was examined for 

 arsenic, using the process employed in the case of examining 

 native bismuth for this substance ; no trace however was found*. 



* I may mention that in analyzing another specimen of this mineral I 

 found 1*90 per cent, arsenic present ; but I satisfied myself that this was 

 due to fine grains of mispickel interposed between the laminae of the 

 mineral. 



