A PRELIMINARY REPORT ON CLAYS OV FLORIDA 111

outcrops in Jackson and Holmes counties where again it forms local residual clay deposits. These residual clays are variable in their physical properties. They range in color from a gray or greenish-gray to a brown, tan or light buff. Sometimes this range of color will be found in a single deposit with the lighter colors at the bottom. They are usually fairly plastic though at times somewhat stiff at the surface, becoming more plastic with depth. In places they are quite sandy and at times contain flint and limestone fragments or calcareous or ferruginous concretions. Red or dark brown-burning clays are the rule, though buff ones are found. Most of these clays have a high air- and fire-shrinkage and also crack and warp badly in drying and burning. The resulting losses are high. The deposits range in depth from a few inches to as much as twenty feet, with a slight overburden, and in lateral extent often cover as much as sixty or eighty acres or more. Some of these clays found in eastern Levy and western Marion and Alachua counties are suitable for common brick. None of the Ocala clays are now being utilized.
 The Marianna formation (Oligocene) is a thin limestone of limited extent in Jackson County. Some very small and local residual clay deposits occur in this area. They will not be treated here, however, on account of their insufficient size and their calcareous character.
 The Chattahoochee formation, also of Oligocene age, occupies an area in the vicinity of the Suwannee and Aucilla rivers, a smail area on the Ocklocknee River, and a belt in west Florida extending westward from the Apalachicola River to beyond the Choctawhatchee River. It consists essentially of a very impure, soft argillaceous limestone with some interbedded clays and marls. Residual clays result from the weathering of this formation and hence are frequently found in the areas where it is exposed. The clays interbedded with the limestone are usually calcareous, greenish to gray in color, break with a slight conchoidal fracture, are fairly plastic, but at times stiff and often very sticky. The residual clay resulting from the decomposition of the Chattahoochee limestone is a plastic joint clay containing some calcareous concretions and geodes. Numerous deposits of it are located in Suwannee and Hamilton counties, in western Gadsden County, and in Jackson and Holmes counties. None of the Chattahoochee clay is now being utilized, although brick plants have formerly been operated near