160 fLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT

 Fire tests:
 Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 0.2 11.02 29.10 Brick red.
 1050 0.3 11.50 28.20 Brick red.
 1150 0.8 11.11 27.10 Gray.
 1190 1.3. 10.22 26.80 Gray.
 1230 1.8 9.73 25.10 Gray.
 1310 2.8 9.60 24.75 Gray.

 The Alum Bluff clays were formerly worked in a number of places in Gadsden County. One plant was operated at Hinson about sixty-five years ago. Plants have also been located near Mount Pleasant, Gretna, Quincy, and Chattahoochee.
 The plant at Quincy worked one of the clays overlying the fuller's earth. This clay is now removed as overburden in mining the fuller's earth and could therefore be used as a by-product. It has medium shrinkage, good working qualities and is suitable for common brick, hollow blocks and drain tile. A vitrified product cannot satisfactorily be made from it, however, as it still has a porous, open texture at cone 15. It has the following physical properties:

 Physical Properties of Floridin Overburden Clay, Quincy (Lab. No. 0-38).
 Plasticity, judged by feel ............ Excellent.
 W ater of plasticity................. 25.65%
 Pore water ........................ 0.50%
 Shrinkage water ................... 25.15%
 Linear air shrinkage................ 12.20
 Volume air shrinkage............... 36.82%
 Modulus of rupture, average........ 315.7 pounds per square inch.
 Slaking test ....................... 2 minutes.
 Steel hard at cone 5.

 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 1.2 11.40 27.85 Brick red.
 1050 1.7 11.10 27.20
 1150 1.8 11.10 27.20
 1190 2.2 10,50 27.10
 1230 2.8 10.50 27.10
 1310 3.7 8.33

 Underlying the northeast part of the town of Chattahoochee and also forming the surface materials at the headquarters of the State Hospital is a deep red, very sandy clay. It is valueless for fired products, but is suitable for sand-clay road metal. As an illustration of this type of clay the following physical properties are given: