102 N.H. Darton — Geology of Florida phosphate deposits. 



The results of I and II agree as closely as could be expected 

 when we consider that each of the three different crystals of 

 II may have, and probably did, represent different molecular 

 mixtures. 



Akt. XII. — Notes on the Geology of the Florida Phosphate 

 Deposits ; by 1ST. H. Daeton. 



During the past year the phosphate deposits of Florida 

 have become of considerable commercial importance and at- 

 tracted widespread interest. As practically nothing was on 

 record as to their geologic relations the writer has devoted sev- 

 eral weeks to a preliminary study of the principal deposits and 

 this paper is a summary of the results. 



The phosphate regions of Florida occur mainly in the west- 

 ern and west-central portions of the peninsula, comprising a 

 series of irregular areas scattered at varying intervals along a 

 narrow belt extending from near Tallahassee towards Gaines- 

 ville and thence nearly to Charlotte Harbor, a distance of 

 250 miles. The entire region is not yet fully explored but the 

 vast extent and commercial importance of the deposits are satis- 

 factorily established and it is safe to predict that Florida will 

 finally become a prominent source of phosphate. The deposits 

 are exceedingly irregular in extent and richness, and while 

 there are many areas underlain by large bodies of high grade 

 mineral, the great number of the deposits consist of impure, 

 thin or scattered beds of no economic value. 



The phosphates are readily separable into three classes : 

 1. Rock phosphate, a homogeneous, more or less completely 

 lithified, light colored phosphate of lime, constituting the sur- 

 face of the middle Tertiary limestone formation. 2. Con- 

 glomerate, consisting of pebbles of phosphate rock imbedded 

 more or less thickly in a matrix of phosphate sand, marl and 

 arenaceous and argillaceous materials. This fragmental forma- 

 tion lies in great sheets on the surface of the limestone, in 

 some cases overlapping the edge of the rock phosphates, from 

 which its pebbles were derived. 3. River drift, consisting 

 of phosphate pebbles derived both from the rock phosphate and 

 the conglomerate and constituting great placer deposits in the 

 stream beds draining the other phosphate regions. 



So far as is known the occurrence of the rock phosphate is 

 restricted to a narrow irregular belt extending through eastern 

 Citrus county, northward through western Marion, probably to 

 the exposures near Albion, and thence with more or less contin- 

 uity through Trenton in Alachua, Steinhatchee in Lafayette 



