74 FERTILITY AND FERTILIZER HINTS 



rock. These phosphates occur in the form of nodules varying in 

 weight from a fraction of an ounce to more than a ton. 



Whether the rocks are mined or dredged, they are washed 

 free from the clay and other adhering matter and dried, 

 when they are ready for shipment. When phosphate rock 

 is ground or pulverized it is known as floats and is 

 used in this form in the middle western states quite extensively. 

 The land rock is light fawn colored; the river rock is black; both 

 are very hard. The South Carolina land rock averages about 50 

 per cent, tricalcium phosphate, which is equivalent to about 23 

 per cent, of phosphoric acid, and the river rock runs about 50 

 to 60 per cent, tricalcium phosphate, which is equivalent to 23 

 to 27.5 per cent, of phosphoric acid. 



Including the year 1908, South Carolina's total production of 

 phosphates was 12,138,454 long tons of rock, of which about 

 one-third was shipped to Europe. The discovery of the Florida 

 phosphates decreased the exportation of those from South Caro- 

 lina, to about 30,000 tons annually, because the Florida phosphates 

 that are exported contain more phosphoric acid and less im- 

 purities.* 



Florida phosphates occur as soft phosphate, pebble phosphate 

 and boulder or hard rock phosphates. The soft phosphate 

 resembles a whitish clay and generally contains 50 to 60 per cent, 

 of tricalcium phosphate, which is equivalent to 23 to 27.5 per cent, 

 of phosphoric acid. The hard rock ranges from 60 to 75 per 

 cent, of tricalcium phosphate, which is equivalent to 27.5 to 34.3 

 per cent, of phosphoric acid, although many samples show even a 

 higher content of phosphoric acid. Most all of the high grade 

 phosphates of Florida are exported to Europe where they find 

 a ready market. Florida has put out 14,087,833 tons of phos- 

 phate rock from 1888 to 1908.* 



Tennessee Phosphates. — These are perhaps the most extensive 

 deposits in the United States that are being worked. Their com- 

 mercial importance was made known in 1893. The Tennessee 

 phosphates are known as brown rock, blue rock and white rock. 

 About one-fourth of the high grade Tennessee phosphate is ship- 



