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FLORIDA GEOLOGICAL SURVEY—15TH ANNUAL REPORT 
Fig. 8. —Clay pit. Gamble and Stockton Brick and Tile Company, South 
Jacksonville, Duval County. Two different beds of clay separated by a 
layer of sand are exposed in this pit. 
The upper red mottled clay has the following physical properties 
Physical Properties of Gamble and Stockton Upper Red Clay (Lab. No. 0 - 58 ). 
Plasticity, judged by feel.... 
Water of plasticity . 
Pore water. 
Shrinkage water. 
Linear air shrinkage. 
Volume air shrinkage. 
Modulus of rupture, average 
Slaking test. 
Steel hard at cone 9. 
Overfires at cone 12. 
Fire tests: 
Excellent. 
23.20% 
1.25% 
21.95% 
8.7 % 
24.2 % 
608.7 pounds per square inch. 
1 hour. 
Temperature. Linear Shr. Absorption. Porosity. Color. 
Per Cent. 
Per Cent. 
Per Cent. 
950°C. 
1.2 
14.58 
32.40 
Brown. 
1050 
1.2 
15.43 
33.00 
Brown. 
1150 
1.3 
14.73 
32.60 
Brick red. 
1190 
1.3 
13.32 
32.00 
Brick red. 
1230 
1.3 
12.61 
27.40 
Brick red. 
1310 
1.5 
12.63 
26.60 
Brick red. 
