CHAPTER IV 



PEBBLE PHOSPHATE ORE DRESSING AND 

 MILLING 



Steam Shovels and Hydraulic Mining Practice 



FLORIDA phosphates, classed as hard rock, soft 

 rock, land pebble, and river pebble, are found in 

 the Eocene, Miocene, and more recent geolcgical 

 formations. The hard-rock phosphates occur 

 massive, laminated, and as boulders piled together, 

 also in the form of pebbles where the other rocks 

 have been broken by weathering and water move- 

 ments. This kind of material possesses a variable 

 structure from compact to fibrous, and while 

 usually of a creamy color is frequently stained 

 with iron oxide. 



The soft rock occurs in deposits by itself and 

 associated with hard rock phosphate. It may be 

 clayey or sandy and fill spaces between boulders of 

 hard rock phosphate. It is evidently a secondary 

 deposit formed by the disintegration of other phos- 

 phates of lime. 



It carries from 20 to 30 per cent less phosphate 

 of lime than hard rock phosphate, which varies 

 from 80 to 85 per cent. 



Land-pebble phosphate is essentially a mass of 

 whitish phosphate pebbles varying in size from 



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