388 Ilillebvand — Occurrence of Nitrogen in Uraninite. 



Branchville was received from Professors Brush and Dana, 

 and was the residue of the material from which Comstock had 

 taken his for analysis, No. VI was by far the purest of any 

 material obtained from any locality. It is earnestly to be 

 hoped that more of this excellent material may be found for 

 closer investigation, since it possesses the greatest density and 

 the highest percentage of U0 3 and X of any known variety, 

 besides representing the extreme of perfection as regards 

 crystallization and purity. 



The Colorado mineral differs from all other American occur- 

 rences in that it is devoid of crystalline form and that thoria is 

 wanting, its place being apparently supplied by zirconia. It 

 moreover contains the least amount of lead of amy known urani- 

 nite. The North Carolina material was analyzed mainly to 

 learn if rare earths enter into its composition. No. X represents 

 the composition of the purest sample available, and No. XI 

 of the residue after extraction of the yellow oxidation products 

 by very weak HC1. Xo really unaltered uraninite appears to 

 have been found in North Carolina. 



Of the Norwegian specimens those analyzed under XII and 

 XIII were from Professor W. C. Brogger, the remainder from 

 Professor A. E. Nordenskiold. XII is the original Broggerite 

 of Blomstrand, while XIII is " so viel ich weiss von derselben 

 S telle wie das Originalmaterial Lorenzens" (Brogger). Those 

 from Professor Xordenskiold all bore erroneously, with excep- 

 tion of that from Arendal, the name Cleveite. 



In the following table all the foregoing analyses of Norwe- 

 gian material have been re-calculated to the percentages found, 

 excluding the insoluble matter, in order that their true relations 

 may appear at a glance, whereby the sum of the rare earths 

 combined is given instead of each earth or group of earths by 





XII. 



XIII. 



XIV. 



XV. 



XVI. 



XVII. 



XVIII. 



uo s 



32-04 



25-48 



26-04 



32-50 



3569 



42-11 



27-12 



TJ0 2 



4825 



50-97 



50-83 



44-57 



43-56 



24-51 



44-71 



Earths 



7-97 



10-18 



996 



1064 



8-12 



13-57 



14-03 



PbO 



9-45 



10-11 



10-14 



9-61 



9-48 



10-66 



11-08 



CaO 



•39 



•77 



•45 



•36 



•41 



1-07 



•62 



H 2 



•77 



•73 



•87 



•78 



•79 



1-23 



1 



H"_._ - 



1-23 



1-28 



1-28 



1-05 



108 



? 



1-26 



itself. Only those constituents are tabulated which may be 

 considered unquestionably in whole or in part as belonging to 

 the uranium mineral. 



An examination of analyses XII to XYI as re-calculated 

 hardly allows of any other conclusion than that the specimens 



