A PRELIMINARY REPORT ON CLAYS OE FLORIDA 
171 
The upper Tampa clay is exposed in several places along the Hills¬ 
borough River and has formerly been worked at Tampa. Both the Tampa 
Northern Railroad and the Atlantic Coast Line Railroad cross exposures 
of this clay. 
The Tampa Brick Company's plant, now abandoned, was located 
about five miles northeast of the city on the Hillsborough River. The de¬ 
posit consists of about ten feet of a light-green plastic clay containing 
numerous cherty concretions. A two-foot overburden- of loose surface 
sand and soil overlies the clay. 
This is a grayish, buff-burning clay which is still distinctly porous 
at cone 15, hence is not suited for any product where vitrification is 
essential. It may, however, be used for common building-brick and 
hollow-block ware. Its physical properties are: 
Physical Properties of Tampa Brick Company Clay (Lab. No. 0-34). 
Plasticity, judged by feel.... 
Water of plasticity. 
Pore water. 
Shrinkage water. 
Linear air shrinkage. 
Volume air shrinkage. 
Modulus of rupture, average 
Slaking test . 1 ... 
Excellent. 
32.45% 
1.05% 
31.40% 
12.80% 
35.85% 
598.2 pounds per square inch. 
5 minutes. 
Fire tests: 
Temperature. 
Linear Shr. 
Per Cent. 
Absorption. 
Per Cent. 
Porosity. 
Per Cent. 
Color . 
950°C. 
0.3 
16.75 
31.50 
Buff. 
1050 
0.3 
16.20 
31.10 
Buff. 
1150 
0.2 
14.18 
29.75 
Buff. 
1190 
2.2 
‘ 14.20 
27.80 
Buff. 
1230 
2.2 
13.25 
27.70 
Buff. 
1310 
13.20 
26.60 
Buff. 
The Temple Terrace Tract, located about six miles northeast of 
Tampa on the Hillsborough River, is underlain by a yellowish and red¬ 
dish, sandy clay which is suited only for sand-clay road material. The 
southern edge of the tract is underlain by the Tampa formation clay 
which has the same properties as the Tampa Brick Company clay 
described in the foregoing paragraph. 
The property of Dr. W. P. Chamberlain, two miles north of Sulphur 
Springs, is underlain by several thin variable clay strata interbedded 
with sand. The clay is of insufficient quantity and at too great depth to 
