A PRELIMINARY REPORT ON CLAYS OF FLORIDA 177

 LEON COUNTY
 Leon County is located in north Florida east of the Ocklocknee River. The Chattahoochee, Alum Bluff, Choctawhatchee and Pleistocene formations are exposed at the surface. A surface mantle of a jointed sandy clay, probably Pleistocene, covers the entire county. Flood-plain clays occur at some points along the Ocklocknee River and lacustrine clays are also found in several places.
 Many years ago, before there were railroads to bring better material from other localities, bricks were made from sandy red clay just north of Tallahassee, and the remains of the yards can still be seen.
 The surface mantle clays occupying the northwestern half of the county and roughly co-extensive with the Alum Bluff formation contain much coarse sand and some gravel. This material is well suited for sand-clay road material.
 The surface material in the southeastern part of the county and essentially co-extensive with the Chattahoochee formation contains a high percentage of clay.
 An exposure of this clay occurs in a road-clay pit about six miles south of Tallahassee on the Woodville road and just north of the Wakulla Hammock. The thickness of this deposit is not known, but more than five feet are exposed. It is overlain by about eighteen inches of surface sand and soil. This clay may be used for a fair grade of common brick, but as it retains a porous texture even at cone 16, it cannot be used for a vitrified product. It has the following physical properties:
 Physical Properties of the Woodville Road Clay (Lab. No. o-5).
 Plasticity, judged by feel........... Fair.
 W ater of plasticity................. 31.40%
 Pore water .................. ....... 1.33%
 Shrinkage water ................... 30.07%
 Linear air'shrinkage ................ 11.3 %
 Volume air shrinkage ............... 29.8 %
 Modulus of rupture, average........ 225.6 pounds per square inch.
 Slaking test ....................... 24 hours.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 9500C. 1.2 17.30 35.00 Buff.
 1050 1.7 18.20 35.00 Buff.
 1150 4.7 14.00 27.80 Buff.
 1190 5.7 13.20 27.80 Buff.
 1230 6.2 11.40 25.90 Gray.
 1310 6.7 10.00 19.30 Gray.
 1370 6.7 9.20 19.90 Gray.
 1430 7.7 8.50 18.60 Gray.