CHAPTER V 



HARD ROCK PHOSPHATE ORE DRESSING AND 

 MILLING 



Loss of Soft Ores Separating the Ores from Clays, etc., 

 and Process of Roasting or Drying 



THAT there is considerable loss of phosphate in 

 mining is well known. Practically all the deposits 

 contain, with other material, more or less phos- 

 phate in a soft or pulverulent condition. Under 

 present methods of mining and treatment this 

 "soft" phosphate is necessarily lost in the proc- 

 ess of washing, being carried to the dump along 

 with the sand, clay, and other constituents of the 

 matrix. The amount of phosphate thus discarded 

 may be expected to vary with different deposits 

 and under different conditions. After reaching 

 the dump there is more or less mechanical separa- 

 tion so that samples taken from one part of the 

 dump may be found richer in phosphate than 

 from some other part of the same dump. Samples 

 taken at random by the writer and analyzed, 

 from some phosphate dumps in the hard rock 

 region gave the following analyses: Total phos- 

 phoric acid, 9.99 to 12.14; which is equivalent 

 to tricalcium phosphate, 21.81 to 26.50. In an- 



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