120 



PROCEEDINGS OF SECTION B. 



The variations in the composition of these minerals will be 

 on comparing the following analysis : — 



*ANALYSIS. 



seen 



Montanite (bismuth-tellurate, Bi, O3 Te O., + H. O (or 2 HjO). 



This mineral was first discovered by Genth during his exami- 

 nation of the tetradymite of Highland in Montana. It is not 

 crystallised, but exhibits here and there, tlie scaly structure of 

 the original tetradymite. 



As Mr. David points out in his description of the minerals, 

 there is a peculiar coloured variety of montanite present, which 

 is of a cubical shape and dark brownish red in colour. A 

 qualitative analysis was made of some of these cubes, and bismuth, 

 tellurium, water, and a considerable quantity of ii'on found 

 to which no doubt the mineral owes its colour. 



On looking over a large number of specimens I succeeded in 

 picking out a few broken pieces of these cubes (about two 

 grammes in weight), though it was found impossible to obtain them 

 thoroughly free from the tetradymite. Tlie following is the 

 result of my analysis : — 



Bismuth Oxide (Bio O3) 50-68 



Tellurous „ (Te O3) 

 Iron Oxide (Fe., O3) 

 Water 

 Gangue (Silica) 



27-65 



14-38 



6-16 



1-00 



99-87 



♦Watt's dictionary of Chemistry, 1883, Vol. V., p. 707. 

 t Impurities. 



