Andrew. — On the Clarendon Phosphate-deposits. 467 



Iron and Alumina. — The large amount of iron and alumina 

 in this phosphate will probably constitute an objection to it in 

 the eyes of the agriculturist. Alumina, when present in a 

 phosphate, is combined with part of the phosphoric acid, the 

 latter being thus rendered unavailable for assimilation by plants, 

 and for conversion into superphosphate of lime ; this happens 

 at Yorke's Peninsula, South Australia,* and in the Lower Green- 

 sand, England! : iron has an effect similar to that of alumina. 

 Moreover, the superphosphate produced when iron and alumina 

 are present is usually sticky and claggy.J The Clarendon 

 phosphate contains a larger amount of these objectionable iron 

 and aluminum oxides than do those of most other countries, 

 as will be seen from the following table. It is with these foreign 

 phosphates that the New Zealand phosphate must compete, 

 if it is to be exported to any extent. 



Excess of Lime. — There is another feature of the chemical 

 composition of these phosphates which, possessing a certain 

 theoretical interest, may be noted here. F. Danvers Power, § 

 in his report on the Ocean and Pleasant Island phosphates, 

 says, " As is always the case, there is an excess of lime (CaO) 

 over the acids present that are capable of combining with it ; 

 supposedly, this excess is an organic combination." Whatever 



* Brown, Rep. Govt. Geologist South Australia, 3rd February, 1902. 



f Penrose, U.S. Geol. Survey Bull. 46, p. 102. 



% Penrose, U.S. Geol. Survey Bull. 46, p. 83. 



§ Danvers Power, " Mineral Industry for 1901," vol. x, p. 533. 



