HARD ROCK PHOSPHATE ORE DRESSING 51 



riveted to the sides of the cylinder is gradually 

 worked from the cold to the hot end, being repeat- 

 edly showered through the hot gases in its passage 

 until discharged. The fuel is coal, wood, or crude 

 petroleum. 



The excess of moisture in the hard rock in this 

 section of Florida during the early years of mining 

 was removed entirely by kiln burning, a process 

 still in use by many operators. For this purpose 

 the phosphate ore is placed on ricks of wood. 

 The wood is then fired, and the phosphates partly 

 smothering the flames permits slow burning, and 

 by the gradual spread of heat, the phosphate be- 

 comes more or less uniformly dried. More re- 

 cently, with the growing scarcity of wood in the 

 hard-rock section several large producers have 

 installed mechanical dryers similar to those used 

 by the land-pebble miners. In a number of in- 

 stances the mechanical dryers are in different parts 

 of the country, and away from the actual mining 

 operations. 



