402 



BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



with an index of refraction for lithium light of 2. 26 ±.02 and for 

 sodium light, 2. 30 ±.02. It seems probable that it is an isometric 

 paramorph after either a tetragonal or an orthorhombic form as 

 many of the complex pegmatite uranium minerals seem to be. Also 

 like nearly all of the complex pegmatite minerals this mineral is 

 variable in composition and the specific gravity of the specimens 

 tested ranges from 4.50 to 5.43 as determined with the Joly bal- 

 ance. The specimens analyzed had a specific gravity of 5.42 (by 

 pycnometer) . 



The radioactivity of specimens of different specific gravities showed 

 slight differences as tested by the exposure of a photographic plate, 

 those having the highest specific gravity appearing most active 

 (pi. 14). The material was not tested with an electroscope. Pieces 

 of like content of uranium and thorium were selected on the basis 

 of comparative radioactivity. Two of the least active pieces from 

 the seventh row (pi. 14) gave on analysis 35 per cent Ti0 2 compared 

 with 39 per cent in the best material. 



If available in quantity this mineral would be of value as a source 

 of radium, but probably only a few pounds could be secured even at 

 prohibitive cost. 



The analysis of such a complex mineral is so difficult that too much 

 weight can not be attached to the percentage figures. The mineral 

 is slowly decomposed by treatment with concentrated sulphuric 

 acid or by hydrofluoric and sulphuric acids. It is more convenient, 

 however, to bring it into solution by gentle fusion with acid sodium 

 sulphate. On dissolving the melt in cold water or dilute sulphuric 

 acid there remains a small residue consisting of silica, unattacked 

 mineral, and sulphates of lead, barium, and strontium. The analysis 

 gave the following results: 



Analysis of brannerite from Stanley Basin, Idaho 

 [R. C. Wells, analyst] 



Silica (SiOs) 



Titanium dioxide (TiOj). 



Ferrous oxide (FeO) 



Lime (CaO) 



Uranium dioxide (UOj)_. 

 Uranium trioxide (UO3)-. 



Thoria(Th0 3 ) 



Ceria (CejOs) 



Yttria earths (YjOs, etc.) 



Zirconia (ZrOj) 



Lead oxide (PbO) 



Barium oxide (BaO) 



Strontium oxide (SrO)... 



Water (HjO) 



Carbon dioxide (COj) 



TotaL 



Molecular 

 values 



0.010 

 .488 

 .040 

 .052 

 .038 

 .116 

 .015 



.011 

 .001 

 .001 

 .002 

 .001 

 .111 

 .005 



