GEOLOGY CHOCTAWHATCHEE AND APALACHICOLA RIVERS. 83 
MINERAL INDUSTRIES. 
BRICK-CLAYS. 
Four brick-making- plants, the Florida Industrial School for 
Boys, at Marianna; Hall and McCormac, Chipley; G. C. & G. H. 
Guilford, Blountstown, and Converse Brick Company, Wetappo are 
located in this area. No clay product other than common building 
brick is at present being manufactured. 
Two samples of clay from this area have been tested in the. U. S. 
Bureau of Mines Clay Testing Laboratory at Pittsburg, Pa. Sample 
No. 1 is from the Florida Industrial School for Boys, Marianna, 
sample No. 2 from the brick plant of Hall and McCormac, Chipley. 
The report of these samples taken from Press Bulletin No. 7 of the 
Florida Geological Survey, is as follows : 
Sample No. 1, Jackson County. The clay works with some difficulty in 
the stiff mud condition ; water of plasticity in per cent of dry weight, 40.80 
per cent ; warped and cracked during the drying treatment ; linear drying 
shrinkage in terms of wet length, 9.95 per cent; linear burning shrinkage in 
terms of dry length, at 850 degrees C., 0.77 per cent; at 1010 C., 4.59 per 
cent; at 1130 C., 6.60 per cent; at 1250 C., 7.55 per cent; color after burning, 
light red at lower temperature, changing to dark red at higher ; per cent poros- 
ity, at 850 degrees C., 36.75 per cent; at 950 C., 40.55 per cent; at 980 C., 34.30 
per cent ; at 1010 C., 30.30 per cent ; at 1040 C., 24.20 per cent ; at 1070 C., 24.00 
per cent; at 1100 C., 26.10 per cent; at 1130 C., 25.15 per cent; at 1160 C., 
23.65 per cent; at 1190 C., 23.60 per cent; at 1220 C., 23.85 per cent; at 1250 
C., 20.70 pe-r cent. A somewhat plastic and sticky clay of high drying and 
burning shrinkage. The clay retains a porous structure at 1250 degrees C. 
(2282 degrees F.), and cannot be used in the manufacture of vitrified ware 
burned in commercial kilns. The clay may be used in the manufacture of com- 
mon and building brick. 
Sample No. 2, Washington County. The clay possesses good working plas- 
ticity and molding behavior ; water of plasticity, 36 per cent ; a few cracks de- 
veloped by drying ; linear drying shrinkage, 9.42 per cent ; linear burning 
shrinkage, at 850 degrees L, 0.55 per cent; at 1010 C., 1.57 per cent; at 1130 
C., 7.75 per cent; at 1250 C., 8.10 per cent. A good light buff color is devel- 
oped by burning; per cent porosity, at 850 degrees C., 36.80 per cent; at 950 
C., 35-30 per cent; at 980 C., 34.75 per cent; at 1010 C., 34.50 per cent; at 1040 
C., 30.75 per cent; at 1070 C., 25.70 per cent; at 1100 C., 22.45 per cent; at 
1130 C., 19.70 per cent; at 11.60 C., 17.95 per cent; at 1190 C, 15.70 per cent; 
at 1220 C., 14.60 per cent; at 1250 C., 12.55 per cent. A buff burning clay of 
good plasticity and a relatively high drying shrinkage. May be used in the 
manufacture of buff colored face brick, although care must be exercised in 
drying. The clay must be burned above 1250 degrees C. in order to attain low 
porosity. 
