

neiv thorium and uranium Mineral. 99 



Upon fusing a portion with sodium bisulphate a solution was 

 obtained and it was thus found to be a silicate containing about 

 23 per cent of uranium oxide (calculated as UO a ), about 46 per 

 cent of thoria and a small per cent of the " rare earths." 



No further data were then obtained from the scant material 

 in hand but its relation to thoro-gummite was made evident. 

 It was among fresh shipments of the various thoria and yttria 

 minerals, made direct from the locality (Llano County, Texas) 

 that this mineral was again found and further analytical work 

 made possible. The new material was unexpectedly found 

 deeply embedded in massive cyrtolite and associated with fer- 

 gusonite. None was found embedded in the new crystals and 

 masses of thoro-gummite. Some fifty kilograms of the broken 

 cyrtolite were thoroughly searched through with the result of 

 finding only about two grams of pure material and this came 

 mainly from one mass, which had a very thin coating of thoro- 

 gummite. A few selected fragments had a specific gravity of 

 5*438, [one portion weighed 0*35 gram.] As the mineral 

 was so scarce it was set aside to await an opportunity when it 

 could be given careful investigation. Later, by using small 

 quantities, the physical characters were made out as follows. 



Description. — The mineral is opaque and black, but not quite 

 so dull in luster as the associated black cyrtolite which it 

 resembles to a very remarkable degree. A strong lens is neces- 

 sary to distinguish the two. Its hardness is about 5*5. No 

 trace of cleavage has been observed. Its fracture is minute 

 sub-conchoidal to hackly. Density = 5438 at 21° C. (for the 

 material analyzed by Hillebrand, see beyond.) Its form, as is 

 often evidenced by the thoro-gummite, is tetragonal and closely 

 resembles zircon and thorite in habit and angle. Square 

 prisms, sometimes l cm thick, with a simple pyramid are all the 

 forms thus far observed. It also occurs massive, nodular and 

 filling veins in cyrtolite and fergusonite embedded in a coarse 

 pegmatite. Under the blowpipe, it is infusible but becomes fis- 

 sured in all directions without intumescence or decrepitation. 



In powder the mineral is not entirely decomposed by any 

 one acid. Sulphuric acid attacks it quite strongly but the gela- 

 tinous silica set free protects it from further action. Hille- 

 brand has observed however that if nitric acid is added, speedy 

 and complete solution results. 



Chemical Composition. — For the chemical investigation of 

 this mineral I am indebted to Mr. W. F. Hillebrand, whose 

 important contributions to the chemistry of uranium minerals 

 are well known. I quote his report and analyses in full. 



" Of the dull black mineral supposed by Mr. Hidden to be the 

 parent of thoro-gummite but nine-tenths of a gram was available 



