A PRELIMINARY REPORT ON CLAYS OF FLORIDA 127

clays are common along the Apalachicola River, one such deposit being worked by the Guilford Brothers Brick Company at Blountstown.
 The Guilford Bros. plant is situated about one-half mile south of Blountstown on a spur of the Marianna and Blountstown Railroad and about one-half mile from a barge landing on the Apalachicola River. Thus both rail and water shipping facilities are afforded.
 The deposit is overlain by soil averaging about six inches in thickness and is underlain in places by sand. The deposit is somewhat lenticular, but averages from four to nine feet in thickness. The clay is dug away from the pit face, then heaped up and allowed to weather for an indefinite time. Sand and mica are present in this clay to a slight extent.
 The clay is at present being used for the manufacture of common brick and at the time the field work was being carried on, brick from this plant was being used in the construction of the Post Office Building at Apalachicola. This clay may be used for face or common brick, drain tile, hollow blocks, flower pots, turpentine cups, ballast, etc. It has the following properties:

 Physical Properties of Guilford Bros. Brick Company Clay (Lab. No. o-6).
 Plasticity, judged by feel ............ Excellent.
 W ater of plasticity ................. 29.75%
 Pore water ........................ 0.93%
 Shrinkage-water ................... 28.82%
 Linear air shrinkage ............... 9.7 %
 Volume air shrinkage .............. 32.20%
 Modulus of rupture, average........ 421.7 pounds per square inch.
 Slaking test ....................... 30 hours.
 Steel hard at cone 1.
 Overfires at cone 16.
 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 9500C. 0.3 17.10 34.00 Brick red.
 1050 0.3 18.20 34.60 Brick red.
 1150 7.3 11.30 26.20 Brick red.
 1190 7.3 6.50 18.50 Brick red.
 1230 7.3 6.35 16.80 Brick red.
 1310 7.8 4.23 16.40 Chocolate.
 1370 7.8 3.4-2 13.10 Chocolate.
 1430 7.8 3.82 14.40 Chocolate.