238 
FLORIDA STAFF, GEOLOGICAL SURVEY. 
To reduce the moisture to the required 3 per cent the producers 
of land pebble phosphate use mechanical dryers entirely. While there 
are several types of these dryers, all consist of a rotary cylinder. 
Heated air and gases of combustion are made to pass through the cyl¬ 
inder from a furnace in front. The wet phosphate rock is fed auto¬ 
matically into the cylinder and by means of varying types of shelving 
riveted to the side of the cylinder is made to pass through, being re¬ 
peatedly lowered through the hot gases in passing, and finally escaping 
at the opposite end. After leaving the cylinder the phosphate is car¬ 
ried by elevator to the storage bin. The fuel used is coal, wood or 
crude petroleum. 
The excess of moisture from the hard rock phosphate in Florida 
during the early years of mining was removed entirely by kiln burning, 
a process still in use by many operators. For this purpose the phos¬ 
phate is placed on ricks of wood. The wood is then fired and the 
phosphate partly smothering the flame permits slow burning, gradual 
spread of the heat, the phosphate being more or less uniformly dried. 
More recently, with the growing scarcity of wood in the hard rock 
section, several of the large producers have installed mechanical dryers 
similar in character to those used by the land pebble producers. 
Phosphates of varying grades and varieties occur in Florida over a 
large territory extending from some distance west of the Apalachi¬ 
cola River east to St. Johns River, and south somewhat beyond the 
Caloosahatchee River. The section of high grade phosphate at pres¬ 
ent productive shown in the maps of plates XI and XII, is included 
within, but comprises a very small part of this area. Phosphates mostly 
of relatively low grade are known at many localities beyond the limits 
of the productive section. A detailed report must await further in¬ 
vestigations. A few of the localities, however, may be mentioned at 
this time. 
River pebble in varying amounts occurs along most of the streams 
flowing from the phosphate sections of the State. 
Hard rock phosphate, aside from the area mapped occurs in La¬ 
fayette, Taylor and Jefferson Counties, various samples having been 
reported from these localities. Analyses of these samples may be 
found in the successive reports of the State Chemist of Florida. 
The calcareous sand of the Alum Bluff formation found at Rock 
Bluff, Alum Bluff and many intermediate localities along the Apalach¬ 
icola River and its tributaries, contains ordinarily a trace of phosphate 
and in some localities is more highly phosphatic. A few samples from 
this section, and coming probably from this formation, have been re¬ 
ceived which contain as much as 44 to 64 per cent of tricalcium phos¬ 
phate, and phosphates of a somewhat higher grade are reported to 
