Uenth.] ^>4: [Oct. 2, 



the general formula : Bi 2 (TeSeSBi)^ and the Cumberland tetradymite 



(I) and the joseite (II) would be : 



I. II. 



Bi 2 S 3 = 34.57 — 15.27 



Bi 2 Se 3 = — 4.04 



Bi 2 Te 3 = 14.19 — 30.72 



BLBi, = 48.84 — 50.17 



97.51 100.20 



It would be interesting if a modification of bismuth of a rhombic form 

 with brachydiagonal cleavage would be discovered, as it would throw 

 some light upon the cause of dimorphism. 



S. Seleniferous Galenobismutite. 



H. Sjogren in 1879 gave the name galenobismutite with the formula : 

 PbS. B^Sj, to a mineral which is found massive and of a somewhat radiat- 

 ing structure at the Ko Mine, Nordmark, Sweden. 



Mr. F. L. Garrison presented me last fall with a specimen of what was 

 considered a selenide of bismuth, which he had received in Fahlun, 

 Sweden, and which was said to have been found a short time ago in that 

 celebrated mine. 



The mineral has one very eminent cleavage, very similar to the brachy- 

 diagonal cleavage of bismuthinite, no other cleavage could be observed ; 

 color, lead gray, but much darker than bismuthinite ; lustre eminently 

 metallic; H = 2. Sp. gr., corrected for the pure mineral, = 7.145. Very 

 brittle. It is associated with quartz, chalcopyrite and pyrrhotite in a rock 

 composed of greenish-black fibrous and radiating hornblende and quartz. 



Unfortunately, only a limited quantity was at my disposal, and the 

 material for analysis could not be obtained in a perfect state of purity, but, 

 as the admixtures were only quartz, chalcopyrite and pyrrhotite, these 

 could be easily calculated and deducted. 



They were : in analysis I, 3.96 % ; in II, 4.25 % ; in III, 5.11 % ; in 

 IV, 8.73%, and in V, 8.80 %. The following results were obtained : 



I. II. III. IV. V. Mean. Atomic ratio. 



Sulphur = 9.71 - not det. - 10.54 - 9.21 - 9.55 - 9.75 - 0.305 1 _ j 94 

 Selenium = not det. 13.65 - 11.20 - not det. 12.43 - 0.156 i 

 Silver) _ 2g 23 _ o 8 18 ~ °- 38 ^ °- 39 - °- 32 - 0.33 - 0.0021 j j 

 Lead > - 28.27 - 27.72 - 27.69 - 27.88 - 0.135 J 



Bismuth = 50.19 - 49.49 - 49.35 - 50.49 - 49.90 - 49.88 - 0.238 2.— 



99.64 100.27 



This gives the formula : Pb (S 2 SeJ. Bi 2 (S^Se^, giving 



3 3 3 5 



Sulphur = 10.43 % 



Selenium = 12.94 — 



Lead = 25.30 — 



Bismuth == 51.33 — 



100.00 



