128 FLORIDA GEOLOGICAL SURVEY— 15 TH ANNUAL REPORT 
CHARLOTTE COUNTY 
Charlotte County is situated in south Florida west of Lake Okee¬ 
chobee. Sands, marls and shell beds occupy the surface exposures, but 
no clay deposits are known at the present time. 
CITRUS COUNTY 
Citrus County is situated in the Hard Rock Phosphate region and 
is underlain mainly by Eocene and Pleistocene formations. Residual 
clays occur locally on the phosphate formations, but they are very ir¬ 
regular in thickness and extent and are subject to excessive cracking 
and warping in drying due to high air-shrinkage, hence are of no value 
for manufacturing purposes. 
clay county 
Clay County lies in the lower part of the St. Johns River valley and 
the eastern half of the county is extensively underlain by flood-plain 
clays. The western half of the county is covered by thick deposits of 
coarse sand with a clay content ranging from 15 to 40 per cent, much of 
which is suitable for sand-clay road metal. The St. Johns River valley 
clays have been used in numerous places for common brick, and one 
plant now operating at Green Cove Springs uses one of the flood-plain 
Fig. 6. —Unloading a kiln. Guilford Bros. Brick Company, 
Blountstown, Calhoun County. 
