A 7 . II. Dai^ton — Geology of Florida phosphate deposits. 103 



and Lauraville in Sewanee, possibly to Monticello, in Jefferson, 

 Perry in Taylor, and some other reported localities in the 

 same direction. This region is not by any means underlain by 

 a continuous sheet of phosphate but includes irregular masses 

 of variable sizes and thickness scattered about in detached 

 bodies often widely separated by barren limestone areas. 



At Dunellon in western Marion county there are representa- 

 tive exposures in the extensive mine openings that are now 

 being worked. Here the phosphate was found outcropping at a 

 number of points in the woods and in low bluffs and reefs in 

 the Withlacoochee river near by. The deposit appears to 

 constitute a large basin of which the bottom was not reached 

 in a thirty-foot pit in the center. The phosphate is in large 

 part a mixture of chalky and flinty rock similar in texture and 

 structure to spongy limonite, but usually creamy white, gray 

 or bluish gray in color. Some portions consist of dense homo- 

 geneous lithified materials, others are spongy, stalactitic or 

 laminated. A fair average sample of high grade mineral was 

 found to contain 83 per cent of phosphate of lime and 4 J per 

 cent of carbonate of lime. 



The Conglomerate phosphates occupy a very considerable 

 area in Florida, and although not as rich in phosphate of lime 

 as the phosphate rock they will be of commercial import- 

 ance. The principal deposits now known are south of the 

 southern termination of the rock phosphate belt, in the west- 

 ern part of Polk county in the vicinities of Bartow and Fort 

 Meade, where they constitute sheets of wide area overlying the 

 limestone, sometimes to a thickness of from twenty to thirty 

 feet. These conglomerate phosphates consist of small pebbles 

 of 80 to 85 per cent phosphate rock, usually light colored, im- 

 bedded in a soft chalky matrix of phosphate sand, carbonate of 

 lime, clay and sand in variable proportions. High grade con- 

 glomerate will average from 73 to 78 per cent of phosphate of 

 lime. 



At intervals along the eastern border of the rock phosphate 

 region and overlapping it at some points there are fragmental 

 and conglomerate deposits of considerable extent but they are 

 much more diverse in composition than the great sheets in 

 Polk county. At the Dunellon mine, northern opening, there 

 is a deposit of this class and the porous, pebbly sandrock — 

 "Chimney rock" of the Gainesville region appears to belong 

 to the same formation. 



The River drift deposits of phosphates are of great eco- 

 nomic importance, for they are rich in phosphate and can be 

 mined at small expense. Nearly every little water course in 

 the phosphate regions contains accumulations of phosphate 



