82 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



however, is not materially affected by the methods employed in 

 removing the overburden, and hence it is not necessary to describe 

 these methods in detail. It may be noted, however, that diverse 

 methods prevail, depending upon the thickness and character of 

 the overburden, the magnitude of the operations and the facilities 

 available. Examples may still be found of removal of overburden 

 by pick and shovel, team and scraper, or team and dump cart. 

 It is, however, only a shallow overburden that can be so re- 

 moved profitably. In the larger mining operations the over- 

 burden is removed by steam shovel, by means of which the 

 material is loaded into cars, which are then drawn to 

 the overburden dump; or the overburden is removed b> the hy- 

 draulic method, the material being pumped through pipe lines 

 to the overburden dump. Whatever method is employed n 

 limited amount of overburden remains with the phosphate rock 

 and must be separated in subsequent treatment. 



Removal of Phosphate from the Pit. — It is not necessary in 

 this connection to describe in detail the methods of removing phos- 

 phate rock from' the pit, since the purity of the rock is but inci- 

 dentally affected thereby. It may be said, however, that the phos- 

 phate rock is either loaded by pick and shovel on wagons or tram 

 cars to be drawn from the pit, or it is taken up by dredge or by 

 hydraulicking. If taken by the hydraulic method the rock is forced 

 through pipe lines to the washer plant. The character of the de- 

 posit determines the methods of removal that may be employed. 

 Where the phosphate is loaded by pick and shovel, such objec- 

 tionable impurities as siliceous boulders, limestone rock and clay 

 balls are rejected at the pit, and in some mines only the coarse 

 rock is taken, leaving the finer phosphate, clay and sand. As a 

 rule, however, there is no attempt to separate the phosphate from 

 the matrix before removal from the pit. 



PREPARATION OF THE PHOSPHATE FOR THE MARKET. 



The phosphate rock mined by the open pit method must be 

 washed and dried. The methods of treatment described in this 

 paper are those followed in America and particularly in the Florida 

 mines. 



WASHING. 



The hard rock phosphate of Florida when brought from the 

 pit is dumped onto a grating of iron bars with 2 or 2^^ inch open- 



