176 
FLORIDA GEOLOGICAL SURVEY—15TH ANNUAL REPORT 
tling, having excellent plasticity but a high air shrinkage. It occurs 
in a bed two and one-half feet thick overlain by six feet of sand. The 
overburden is too heavy for a clay of that thickness to be of commercial 
importance. 
The Keystone Brick Company at Whitney works a lacustrine de¬ 
posit ranging from seven to twelve feet in thickness and overlain by 
about eighteen inches of sand. The clay is also underlain by sand. Two 
pits about sixty yards apart have been opened. The clay in one of these 
is a little more sandy than in the other. 
A good grade of common brick is made which is shipped to markets 
throughout peninsular Florida. Tampa and St. Petersburg use the 
greater part of the output. This plant is located on a branch of the Sea¬ 
board Air Line Railway. The Keystone brick, while not particularly a 
semi-refractory product, is widely used in South Florida for fire-box 
lining under boilers. 
This clay retains a soft, porous texture at cone 15 and may be used 
only for common building-brick. Its physical properties are: 
Physical Properties of Keystone Brick Company Clay (Lab. No. 0 - 54 .). 
Plasticity, judged by feel. 
Excellent. 
Water of plasticity. 23.90% 
Pore water.. 1.58% 
Shrinkage water. 22.40% 
Linear air shrinkage. 10.9 % 
Volume air shrinkage. 32.3 % 
Modulus of rupture, average. 491.3 pounds per square inch. 
Slaking test 
Fire tests: 
Temperature. 
950°C. 
1050 
1150 
1190 
1230 
1310 
Linear Shr. 
Per Cent. 
0.6 
1.1 
1.1 
1.6 
2.1 
2.6 
A bsorption. 
Per Cent. 
19.84 
11.49 
9.43 
9.78 
9.69 
8.40 
5 minutes. 
Porosity. 
Per Gent. 
33.40 
30.20 
26.90 
26.50 
24.20 
' 23.50 
Color. 
Brick red. 
Brick red. 
Brick red. 
Brick red. 
Brick red. 
Brick red. 
Another brick plant was formerly operated near Whitney by the 
Whitney Brick Company. The deposit was a sandy lacustrine clay, 
from which a red common brick was made. 
LEE COUNTY 
Lee County lies between Lake Okeechobee and the Gulf of Mexico 
and is underlain by sands, marls and limestones of Pleistocene age. No 
clays of importance are known. 
