PIIOSPHATIC MANUEES 211 



The former is obtained by dredging the river beds, and 

 the latter by mining ashore. The river phosphate gener- 

 ally contains a somewhat larger proportion of iron and 

 alumina than the land phosphate, but in other respects 

 they are much alike. The South Carolina deposits were 

 discovered about forty years ago, and those of Florida 

 some twenty years later. Both have proved enormously 

 productive. The Florida phosphates are much the richer 

 of the two. The land phosphate contains 70 to 80 per 

 cent., and the river phosphate about 60 per cent, of tri- 

 calcic phosphate. The best quality of Charleston phos- 

 phate, after grading, contained only 60 per cent. 



Belgian and Somme phosphates differ from those pre- 

 viously mentioned in their mode of occurrence. On the 

 Franco-Belgian frontier there is found a great deposit 

 of friable phosphatic chalk called " craie-grise," lying 

 on a bed of ordinary white chalk. It extends over an 

 area of some seven million acres and is chiefly worked 

 near the town of Mons, in Belgium, and in the Somme 

 and Pas de Calais departments of France. The phosphate 

 exists in the form of yellow crystalline grains embedded 

 in the chalk matrix which, in the crude state, contains 

 from 20 to 30 per cent, of tricalcic phosphate. In the 

 upper layers pockets are often found containing a larger 

 proportion of this phosphatic sand and less calcium 

 carbonate than the main bulk. These pockets are found 

 chiefly on the French side. The chalky matter is much 

 softer than the phosphatic grains and a large proportion 

 of it can be got rid of by processes of grinding and sifting. 

 The proportion of phosphates is thus raised far above 

 that found in the crude product. The Sornme phosphate 

 is graded and sold in different qualities varying from 

 60 to 80 per cent. It should not be confused with the 

 Bordeaux or Lot phosphate, though both are sometimes 

 naturally spoken of as French. The Belgian phosphate 



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