Mhieralogical Notices. 37 



Aiialysis of the Bornine of Brazil {Telluret of Bismuth) ^ hy 



M. A. Damour. 

 The bornine, the analysis of which I present, is in mica- 

 ceous laminae having the brilliancy of polished steel, slightly 

 flexible, and very thin ; heated on charcoal it fuses, becoming 

 surrounded with a white ring and a green ring, and finally 

 disappears in the pores of the charcoal. 



In the open tube it fuses on the first application of heat, 

 disengages a sulphurous smell, then white fumes of oxide of 

 tellurium, and toward the close of the operation a marked 

 smell of selenium. In the upper part of the tube a white crust 

 is observed surmounted by a light brick-red layer, attributable 

 to the condensation of the selenium. The lower part of the 

 tube remains covered with a yellowish residue of oxide of bis- 

 muth. 



Nitric acid dissolves it very easily with a disengagement of 

 nitrous gas; analysed by this means the bornine of Brazil has 

 given the following results : — 



Relations. 

 1561 

 30J 



Tellurium . . 15*93 198 3 



Bismuth . . . 79-15 594 8 



99*71 



In taking the number 1330*376, adopted by MM. Regnault 



and Rose, as the atomic weight of bismuth, and that of 802*131 



for the atomic weight of tellurium, the preceding results might 



be expressed by the formula 



Bi2 S2 + 3Bi2 Te. 

 This composition differs considerably from the results ob- 

 tained by MM. Berzelius and Wehrle for the bornine of 

 Chemnitz, as well as those which the bornine of Deutsch- 

 Pilsen yielded to the latter chemist. 



These differences might perhaps lead us to adopt three 

 species of bornine, but we rather think that, if tellurium 

 and bismuth can combine in exact proportions, they may also 

 combine in very variable quantities. To decide this delicate 

 question — one too which occurs with many metallic minerals 

 — it is necessary to wait until crystals of bornine combine the 

 two characters which determine the formation of mineral spe- 

 cies, namely the atomic composition and the crystalline form. 



Sulphur . . . 3*15 ^u^ , 

 Selenium ... 1-48 «^ ^186 J 



