HARD ROCK PHOSPHATE ORE DRESSING 45 



other case, a sample of floats from the dumps in the 

 land pebble section gave as follows: total phos- 

 phoric acid, 11.47; equivalent to tricalcium phos- 

 phate, 25.04. In still another analysis made of the 

 plate-phosphate ore, it was as follows: silica, 

 58.95 to 60.10; iron and alumina, 11.70 to 11.20; 

 calcium phosphate 26.80 to 27.92. It is estimated 

 in this particular case that approximately four tons 

 of material was excavated and washed in order to 

 obtain one ton of the high grade rock phosphate 

 (77 per cent). From this it is evident that of the 

 material taken from the pit three-fourths, carry- 

 ing about 27 per cent calcium phosphate, goes to 

 the dump, while one-fourth, carrying 77 per cent 

 calcium phosphate, is saved; thus of the total 

 phosphate ore taken from the pit, in this instance 

 at least, one-half goes into the dump. 



From these data it is apparent that a large 

 amount of phosphate ore is being lost annually in 

 this section and that any economical method of re- 

 claiming this waste or of utilizing the floats, if such 

 be devised, are clearly of the greatest importance 

 to the phosphate industry, and ultimately to the 

 agricultural interests of the whole country. 



With the extension of agriculture necessary to 

 support increased population, together with the 

 progressive exhaustion of the new and naturally 

 rich soils, there arise increased demands upon the 

 phosphate supply. At the present this demand is 

 coming mostly from the older countries of Europe, 

 and the phosphate now produced is largely ex- 



