232 
FLORIDA GEOLOGICAL SURVEY—I5TH ANNUAL REPORT 
Fig. 50.—Empty settling vat. Florida China Clay Company, 
Okahumpka, Lake County. 
Chemical Analysis of Washed Clay from Edgar. C. Langenbeck, Analyst. 1 
Silica (SiC> 2 ) . 
Alumina (AI 2 O 3 ) . .. 
Ferric Oxide (Fe 2 C> 3 ) 
Lime (CaO) . 
Magnesia (MgO) ... 
Alkalies (Na 2 0, K 2 0) 
Water (H 2 0) . 
45.39 
39.19 
0.45 
0.51 
0.29 
0.83 
14.01 
Total 
100.67 
MINERALOGY 
Somers 2 studied samples of the Florida sedimentary kaolins micro¬ 
scopically and found kaolinite to be abundant, hydromica, fairly abun¬ 
dant ; and a few grains of rutile, chlorite, and zircon to be present. He 
reports that sillimanite was developed in one of the test pieces fired at 
1150° C. where the conditions happened to be favorable for its develop¬ 
ment. He believes it to have been formed from the large flakes of kaolin¬ 
ite or low-grade hydromica. 
USES 
The Florida sedimentary kaolin is used almost exclusively in the 
white-ware industries. Its principal uses are in making pottery, decora¬ 
tive tile, spark plugs, and electric porcelain. 
1 Chemistry of Pottery, p. 100 . 
2 Somers, R. E., Microscopic Study of Clays included in U. S. Geol. Survey, 
Bull. 708, p. 292, 1922. 
