267 



Chemical Notes on Davidite 



By W. T. Cooke, D.Sc, University, Adelaide.- 

 [Read August 10, 1916.] 



A preliminary note by Professor Rennie and myself on 

 -certain radio-active minerals from Olary appeared in these 

 Proceedings in the year 1906. Of the ferriferous and titan- 

 iferous radio-active constituents of the lode, the one referred 

 to as Davidite is the most interesting, as it is homogeneous 

 and is a distinct species (vide "Mineral Notes," by Dr. Maw- 

 son, in this volume, p. 262). The bulk of the lode, however, is 

 a mechanical and chemical mixture of ilmenite, magnetite, 

 .rutile, and davidite. 



Analyses of davidite gave the following figures: — 



Ti(X 54-3 



FeO 

 Fe 2 3 



Rare earths 

 V 2 5 , Cr 2 3 

 MgO 

 CaO ... 

 PbO ... 

 CuO ... 

 H,0 ... 



and 



u 3 o 8 



16-0 

 130 

 8-3 

 4-6 

 0-6 

 1-5 

 11 

 trace 

 1-5 



Total 100-9 



The rare earths contain very little thorium, but much 

 cerium. The presence of lanthanum, did3nriium, erbium, and 

 yttrium was shown by chemical and spectroscopic tests. Most 

 of the 4'6 per cent, included under vanadium, chromium, and 

 uranium oxides is due to the last-named element. 



Zirconium is absent. 



Scandium. — Sir William Crookes has by spectroscopic 

 analysis found that scandium is present. $■) 



Davidite readily gives off helium in quantity when heated 

 tfco a red heat; 100 grams yielding about 15 cubic centimetres 

 of fairly pure helium. 



'(l) Private communication from Dr. Mawson. 



