RADIOACTIVE MINERALS IN SOUTH AFRICA. 



By Prof. Paul Daniel Hahn, M.A., Ph.D. 



(Plates 12-14.) 



During the last eight years the author has examined a large 

 uuml)er of South African minerals with regard to radioactivity. 

 Up to the present six distinct minerals have heen observed to 

 be radioactitve. z'ic, monazite, jeschynite. euxenite, fergusonite, 

 carnotite with uranium ochre, and pitch-blende. The radio- 

 activity in these minerals is due either to the presence of 

 uranium or thorium. The minerals which were found to be 

 radioactitve were also analysed to determine the amounts of 

 uranic trioxide and tboric dioxide; in none of the minerals 

 that were analysed were uranium and thorium found together.* 



Monazite. 



The minerals containing the rare earths were considered 

 <luring last century purely from a scientific point of view, prin- 

 cipally because thev had been observed only in very few locali- 

 ties : they were difficult to obtain, and the constituent elements 

 did not appear to be of any practical use. The nature and com- 

 position of these minerals had been chiefly investigated by 

 Swedish and Danish chemists. When it was found that some 

 of tlie constituents of these minerals were of special value in 

 the manufacture of incandescent lamps, search for them was 

 made everywhere. It soon became evident that the occurrence 

 of these minerals was by no means limited to Norway and 

 Sweden. In the United States as well as on the coast of 

 Brazil, near Bahia, large deposits of some of these "rare" 

 uiinerals were discovered. Of these, the mineral monazitet is 

 of special interest. It is essentially a phosphate of eerie and 

 lanthanic sesquioxide. Its value, however, depends upctn the 

 amount of thoric dioxide, which occurs in monazite as an 

 accessory " impurity," sometimes up to 9 per cent. Until 1895 

 most of the monazite was obtained from Norway, and from 

 North and South Carolina, in the United States. Since 1895 

 Brazil has supplied the demand of Europe. The production of 

 monazite in the United States Avas : — 



In 1893 — 59 tons, value £1,600. 

 In 1894 — 340 tons, value £9,500. 

 In 1895 — 862 tons, value £24,000. 

 In 1896 — 8 tons, value £175. 



* Tt is weil known that some pitchblende contains as much as 6 per 

 cent, of thoric dioxide. 



fThe reader will find a description *of this interesting mineral in any 

 "handbook on IMineralogy. 



