122 GEOLOGY OF OHIO. 



(d. <?./.)— c - c - Wares, White, Granite and China. 



The three kinds of wares included in this list, which constitute the 

 different varieties of white pottery, are all closely allied and are all of 

 them so little connecte d with the mineral resources of the state that it 

 has been considered best to treat them together. 



The materials from which white pottery is made comprise a good 

 many other articles than clays. 



Clays however constitute the base of the mixture and as may be 

 eypected only the purest and whitest varieties can be used. 



In earthen, stone and yellow wares we have seen how the careful 

 attention of the potter must be directed to the clays which constitute his 

 body material. 



We have seen that these clays contain a clay base mixed with silica 

 and fluxes in varying proportions, and that the potter is compelled t -> 

 search among the mineral deposits for these clays in which the proportion 

 of sand and flux are naturally united to secure the ends which he has in 

 view. 



In making the body mixture for white pottery, the process is reversed. 

 The potter's skill is now directed to compounding a body from its 

 elements, which, when ultimately finished, shall possess all of the qualities 

 which an exacting market demands. 



The clays for his purposes are limited to those of a pure nature. 

 Every tinge of iron or impurity which goes into his wares is to be cor- 

 rected only by the use of expensive chemicals. 



The china clays or kaolins of commerce come from very many sources. 

 Every state which carries the Appalachian mountain range across it, con- 

 tributes more or less to the supply of pure kaolin and Kentucky, Indiana, 

 Texas and other localities are producing more or less of this mineral. 

 The best or at least the most expensive clays are imported from abroad. 

 Ivarge quantities come annually from England, Germany and other coun- 

 tries. 



Ohio, has so far failed to produce or indicate the presence of one 

 pound of pure white clay. The geological formation of our state contains 

 only sedimentary formations. No granite or feldspathic rocks occur on 

 the surface any where in the state and we naturally therefore expect to 

 find only such clays as are formed elsewhere and are brought here mingled 

 with the detritus of many other rocks. 



The clays brought into the state for pottery purposes are many of 

 them devoid of much plasticity and the potters find the need of a tough, 

 waxy, thoroughly plastic clay. To fill this want, the ball clays are used, 

 some from this country but the majority brought over from England. 



To counteract the excessive shrinkage of these pure clays the potter 

 uses what he calls "flint." It is practically pure silica, being made out of 

 the finest' white sand, ground to an impalpable powder. But silica, in 



