266 



of several months, coated more or less with mustard-yellow 

 carnotite. A sooty coating in two fissures in the lode, and" 

 also smearing some of the coarse biotite, was found to be 

 very highly radio-active. In appearance the coating sug- 

 gested oxide of manganese. It completely dissolves in weak 

 acid. A rough test showed it to be almost entirely oxide of 

 uranium. This apparently is the first report of the occur- 

 rence of uranic oxide free in nature. The formation of the 

 carnotite at the surface, in the dump heap, appears to depend 

 upon the presence of this uranic oxide in the gangue. In the 

 surface portions of the lode a micaceous mineral in tiny green 

 scales occurs in places. At the time of writing the pre- 

 liminary note < 5 ) it was suggested that this might prove to be 

 roscoelite. Examination is hampered by the minute quantity 

 available, but it certainly is not roscoelite, inasmuch as the 

 absence of vanadium has been proved. Uranium also is 

 absent, but it does contain 6 '8 per cent, of Cr 2 3 (chromic 

 oxide). The 16 lb. block of lode matter which formed the 

 basis of the report (6> by T. Crook, F.G.S., and G. S. Blake, 

 B.Sc, F.C.S., contains no typical davidite that can be 

 observed by the naked eye. Their reports deal comprehen- 

 sively with what the block sample contained — namely, carno- 

 tite and the massive non-homogeneous radio-active ilmenite, 

 which composes the body of the lode. ( 7) It may be also that 

 the block contains some davidite in microscopic quantities. 

 As already mentioned, davidite occurs elsewhere in the lode 

 in the form of rough crystals, which are microscopically 

 homogeneous. The conclusions of Crook and Blake that 

 davidite is a non-homogeneous substance is, therefore, not 

 valid. 



Trans, and Prof. Roy. Soc. S. Aus., 1906. 



(6) "On Carnotite and an associated minora! complex from 

 South Australia," Min. Mag., March, 11)10', vol. xv. 



(7) Note made upon personal inspection of the block. — D. M. 



