Thoria Minerals from Llano County, Texas. 481 



acid. We name this mineral thoro-gummite, because it is a 

 gummite in which the water has been replaced by the thorite 

 molecule. 



jSTivenite, a hydrated ihorium-yttrium-lead toranate. 



This mineral we found intimately associated with fergusonite 

 and thoro gummite. It is as yet a rare mineral at the locality. 

 Its specific gravity is 8*01. H. =5-5. It is velvet-black in 

 color and when powdered becomes brown-black. After ignition 

 it turns blue-black. As yet only massive pieces have been 

 found, but some of these suggest that the species may be iso- 

 metric in crystallization. It is easily soluble in nittic and 

 sulphuric acids and some slight effervescence* was noticed 

 upon dissolving the mineral. The analysis gave the following 

 results : — 



Oxygen ratio. 



U0 3 46-75 48-69 = 12' 



UOo 19-89 14-62 ) 



ThO a T-57 5-74 j 



To0 3 , etc 11-22 Atomic weight 124-2 11-34 J-37-33 = 9-20 



Fe 2 3 0-58 1-08 | 



PbO 10-16 455 J 



(Ignition) loss H 2 2-54 14-11= 3-48 



Insoluble 1-22 



9993 



The ratios found lead to the general formula 9RO, 4U0 3 , 

 3H 2 in which RO may be replaced by its equivalent in R 2 0, 

 and R0 2 . If the iron be calculated as protoxide and a corres- 

 ponding increase be made in the amount of uranic oxide, the 

 ratio for U0 3 : RO : H 2 becomes 12 : 8-74 : 3*40. As it is not 

 possible to determine the state of oxidation of the iron in pres- 

 ence of the two oxides of uranium, by any process known to us, 

 we cannot give the exact ratio, as it exists, but would point out 

 that if only 033 per cent of ferric oxide is present and the rest 

 of the iron is present as protoxide, then the ratio of U0 3 to 

 bases will be exactly that which is required by the formula. 



This mineral is allied to the rare species cleveitef and brog- 

 gerite4 and we give below the analyses with the formulae 

 which we have calculated from them, so that the points of dis- 

 tinction may be made evident. 



* Cf. Hillebrand, who has identified nitrogen in uraninite. This Journal, 

 Oct., 1889, p. 329. 



f Dana's Appendix, III. p. 28. 



% This Journal, June, 1884, p. 493. 



