THE PEBBLE PHOSPHATES OF FLORIDA. 
E. H. SELLARDS. 
The phosphates of Florida are known commercially as hard rock, 
land pebble, and river pebble. An explanation of the origin of the 
hard rock phosphate was suggested by the writer in a paper published 
in 1913*. The present paper relates to the origin, location and con¬ 
ditions of deposition of the land and the river pebble deposits of the 
State. 
LOCATION OF DEPOSITS. 
The land pebble phosphate deposits of Florida known to be 
workable are found in southern Florida, in Hillsboro, Polk and De- 
Soto counties. The belt of country in which mines are now operat¬ 
ing extends from near Plant City on the north to near Bowling 
Green on the south, a distance in a north-west to south-east direction 
of approximately thirty miles. The width of the productive belt 
probably nowhere exceeds ten or fifteen miles. The formation, of 
which these workable beds are a part, has, however, as will be 
shown, a much greater extent. 
The term river pebble is applied to phosphates that have accumu¬ 
lated along streams. The best known of the river pebble deposits 
and the only ones that have been worked commercially are those 
found in the valley of the Peace River in DeSoto County and in 
the valley of the Alafia River in Hillsboro County, although smaller 
deposits are known at many other localities in the State. 
The hard rock phosphate deposits are found in north central 
Florida forming a belt paralleling the Gulf Coast for a distance of 
about 100 miles. The approximate location of the different types 
of phosphate in Florida is shown on the accompanying outline map. 
Phosphate mining in Florida was begun on Peace River in 1888, 
the first rock produced being river pebble; in that year, also, the 
hard rock phosphates were discovered and were rapidly developed. 
Production of land pebble phosphate in Florida was begun probably 
in 1890, the first shipment having been made in 1891. No river 
pebble is now being mined in Florida; of the hard rock phosphate the 
output for some years past has approximated one-half million tons 
per annum, while of land pebble, the production at the present time 
under normal conditions is in excess of two million tons per annum. 
*Fla. State Geol. Surv., 5th Ann. Rept., pp. 23-80, 1913. 
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