124 rLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT


 A brown sandy clay occurs in numerous places in the region just west of Gainesville. Here the clay at times immediately overlies the Ocala limestone and at other times is underlain by a sand. It can only be used for a low-grade, soft, porous common brick. A common-brick plant was formerly operated about two miles northwest of Gainesville. A sample from the property of D. J. Richbourg, four miles southwest of Gainesville, has the following physical properties:

 Physical Properties of D. J. Richbourg Clay (Lab. No. o-45).
 Plasticity, judged by feel ........... Fair.
 W ater of plasticity ................ 23.90%
 Linear air shrinkage ............... 4.5 %
 Volume air shrinkage .............. 22.55%
 Modulus of rupture, average........ 255.4 pounds per square inch.
 Slaking test ....................... 5 m minutes.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 9500C. 1.0 15.07 36.10 Brick red.
 1050 1.5 16.44 34.10 Brown.
 1150 1.5 15.77 33.90 Brown.
 1190 2.2 15.67 32.40 Chocolate brown.


 Some residual clays from the Ocala limestone occur in the southwest portion of the county. These warp and crack badly and hence are practically unusable.
 BAKER COUNTY

 Baker County is located in the northeast part of the State. The surface materials consist of yellow and brownish sandy clays and sands, with the Alum Bluff formation underlying much of this loose material. The clays are of little value from a commercial standpoint. A clay which occurs about a half-mile southeast of Macclenny on the Maxville road was formerly used for common brick, but only a soft, porous, sandy common brick can be made from it. Its physical properties are:

 Physical Properties of Macclenny Clay (Lab. No. t -6x).
 Plasticity, judged by feel............ Excellent.
 W ater of plasticity ................ 21.40%
 Pore water ....................... 0.38%
 Shrinkage water ................... 21.02%
 Linear air shrinkage ............... 7.1 %
 Volume air shrinkage .............. 15.6%
 Modulus of rupture, average........ 105.2 pounds per square inch.
 Slaking test ....................... 1 hour.