CLAYS OF NEW YORK 621 



Missouri^ 



The clays of Missouri belong to the following classes: 



Chinaware clays 



Flint clays 



Plastic fire clays 



Pottery or stoneware clays 



Shale, and brick clays " ■ 



Chinaware clays. The Missouri kaolins south of the Missouri 

 river are of Paleozoic age. The belt is worked in Cape Girardeau 

 and . Bollinger co. and extensively in Howell co. The Mis- 

 souri kaolins are residual, and the interesting feature about them 

 is that they have been derived from the decay of aluminous lime- 

 stone, whereas the igneous rocks of the region furnish only impure 

 chinaware clay. The Missouri kaolin is generally highly silicious 

 in its composition, but this is not exceptional. 



Flint clays. The flint clays of Missouri often approach closely in 

 composition to kaolinite. They occur in the central part of the 

 state, being abundant in the counties of Warren, Montgomery, 

 Calloway, Osage, Franklin, Crawford and Phelps. The geologic 

 age may be Carboniferous, Silurian or Ordovician. They form a 

 cradle-like deposit in the limestone which has a depth of 50 to 200 

 feet, and 15 to 50 feet. Most of them have less than 2^ of im- 

 purities. They have from SOfo to 43^ of alumina, and 14^ to 15^ of 

 combined water, thus resembling kaolinite in their composition. 

 They are devoid of plasticity, and in use have to be mixed with 

 plastic clays. They generally begin to fuse at a temperature of 

 2300°, but do not become viscous under 2700°, and are therefore 

 fairly refractory. 



Plastic fire clays. All of these occur in the Carboniferous, asso- 

 ciated with seams of coal. They are generally massive, dense, hard, 

 and plastic. Those around St Louis are specially important and 

 form the base of the enormous local development of the clay-work- 

 ing industry. 



1 Mo. geol. surv., 11. H. A. Wheeler. Clays of llissouri. 



