194 FLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT

 Fire tests:
Temperature. Linear Shr. Absorption. Porosity. Color.
 Per Cent. Per Cent. Per Cent.
 950*C. 3.1 8.92 23.20 Salmon.
 1050 3.1 9.10 21.50 Salmon.
 1150 4.1 8.25 20.45 Gray.
 1190 4.1 7.45 16.00 Gray.
 1230 5.1 6.60 14.50 Gray.

 PINELLAS COUNTY
 Pinellas County is located on the Pinellas Peninsula, which lies between Tampa Bay and the Gulf of Mexico. It is underlain by sands and marls with some interbedded clays of the Tampa, Alum Bluff and Caloosahatchee formations.
 Some phosphatic clays are exposed on the Gulf coast and in Curlew Creek north of Dunedin. These are not suited for use in the manufacture of burned products.
 A gray, sandy clay is found near Alligator Creek, one-half -mile west of Coachman on the Tampa and Gulf Coast Railroad. The clay is approximately twenty-four feet thick and is overlain by three feet of sand. This clay may be used for the manufacture of a fair grade of common brick. A vitrified product, however, could not be produced.
 A bluish-gray clay is exposed at the edge of Old Tampa Bay and extends around to the vicinity of Safety Harbor. This clay contains organic matter and some soluble salts and swells badly upon firing.

 POLK COUNTY
 Polk County is situated in the south-central part of the peninsula. The Alum Bluff and Bone Valley formations comprise the chief surface materials. The northern and eastern part of the county has a heavy coating of coarse, sandy clay, suitable only for sand-clay road material.
 The Bartow clay, the sandy clay stratum overlying the Land Pebble Phosphate horizon, is of widespread occurrence in the southwestern part of the county. The term, Bartow clay, was formerly applied to the matrix carrying the pebble phosphate, but now the application of this term is limited to the sandy clay overlying the phosphate horizon. It is removed as overburden in the phosphate mines of this region.
 The Bartow clay ranges in thickness from three to twelve feet. Its high sand content renders molding and handling difficult. This clay may be used only in the manufacture of common brick. It makes a porous,