194 FLORIDA GEOLOGICAL SURVEY—I5TH ANNUAL REPORT 
Fire tests: 
Temperature. 
Linear Shr. 
Per Cent. 
A bsorption. 
Per Cent . 
Porosity. 
Per Cent. 
Color. 
950°C. 
3.1 
8.92 
23.20 
Salmon. 
1050 
3.1 
9.10 
21.50 
Salmon. 
1150 
4.1 
8.25 
20.45 
Gray. 
1190 
4.1 
7.45 
16.00 
Gray. 
1230 
5.1 
6.60 
14.50 
Gray. 
PINELLAS COUNTY 
Pinellas County is located on the Pinellas Peninsula, which lies 
between Tampa Bay and the Gulf of Mexico. It is underlain by sands 
and marls with some interbedded clays of the Tampa, Alum Bluff and 
Caloosahatchee formations. 
Some phosphatic clays are exposed on the Gulf coast and in Curlew 
Creek north of Dunedin. These are not suited for use in the manufac¬ 
ture of burned products. 
A gray, sandy clay is found near Alligator Creek, one-half mile 
west of Coachman on the Tampa and Gulf Coast Railroad. The clay is 
approximately twenty-four feet thick and is overlain by three feet of 
sand. This clay may be used for the manufacture of a fair grade of 
common brick. A vitrified product, however, could not be produced. 
A bluish-gray clay is exposed at the edge of Old Tampa Bay and 
extends around to the vicinity of Safety Harbor. This clay contains 
organic matter and some soluble salts and swells badly upon firing. 
POLK COUNTY 
Polk County is situated in the south-central part of the peninsula. 
The Alum Bluff and Bone Valley formations comprise the chief surface 
materials. The northern and eastern part of the county has a heavy 
coating of coarse, sandy clay, suitable only for sand-clay road material. 
The Bartow clay, the sandy clay stratum overlying the Land Pebble 
Phosphate horizon, is of widespread occurrence in the southwestern 
part of the county. The term, Bartow clay, was formerly applied to 
the matrix carrying the pebble phosphate, but now the application of this 
term is limited to the sandy clay overlying the phosphate horizon. It is 
removed as overburden in the phosphate mines of this region. 
The Bartow clay ranges in thickness from three to twelve feet. Its 
high sand content renders molding and handling difficult. This clay may 
be used only in the manufacture of common brick. It makes a porous, 
