PHOSPHATE DEPOSITS OF THE SOUTHERN STATES. 8^ 



has a bluish cast^ and is more or less phosphalic. The age of this 

 underlying limestone is Ordovician. 



FLORIDA. 



The phosphate produced in Florida includes, as previously 

 Stated, two kinds, namely, hard rock and land pebble phosphates. 



The matrix in which the hard rock phosphate is imbedded is 

 extremely variable. The formation includes a mixture of materials 

 from various sources and of the most diverse character, further 

 complicated by pronounced chemical activity within the formation 

 itself. The prevailing phase of the formation is feebly coherent, 

 more or less phosphatic, lig'ht gray sand. Aside from these sands 

 the principal materials of the formatioii are clays, phosphate rock, 

 flint boulders, limestone inclusions, pebble conglomerate, erratic 

 and occasional w^aterworn flint pebbles, vertebrate and invertebrate 

 fossils, and occasional pieces of silicified tree trunks. 



The gray sands may be observed in every pit that has been 

 excavated in this section. Moreover, from drill and prospect holes 

 •t is known that these sands occur very generally over the inter- 

 \-ening or barren area. The sands are of medium coarse texture, 

 the grains being roughly angular. The amount of phosphate asso- 

 ciated with these sands is variable. When affected by slow decay 

 and by water, carrying more or less iron in solution^ they become 

 reddish or ochre yellow in color. Lithologically these sands re- 

 scm])le closely the gray phosphatic sands of the Alum Bluff forma- 

 tion as seen at the type locality at Alum Bluff, on the Apalachi- 

 cola River. 



The clays in this formation occur locally as clay lenses im- 

 bedded in the sand, or separating the sand from the phosphate rock, 

 or overlying the phosphate rock. The clays are often of a light 

 buff or blue color. When lying near the surface, however, they 

 often oxidize to varying shades of red. The relative amount of 

 clay in the phosphate-bearing formation increases in a general way 

 in passing to the south. The exposures in the southern part of 

 the area show as a rule more clay than do similar exposures in the 

 northern part of the area. The phosphate boulders seem to have 

 a tendency to group around and to be associated with local clay 

 lenses. Frequently the productive pit gives place laterally to 

 barren gray sands. 



