52 



GEOLOGY OF OHIO. 



High Grade Ci,ays. - 



f 1. Kaolin. * 



2. China clay. 



3. Porcelain clay. 



4. Fire clay (hard). 



5. Fire clay (plastic). 



6. Potters' clav. 



Low Grade Cxays. ■ 



1. Argillaceous shale 



2. Ferruginous shale 



3. Silicious clays. 



4. Tile clays, 



Uses. 

 Manufacture of fine ware. 



(( (( « t( 



Refractory materials. 

 Earthenware, etc. 



Uses. 

 Paving block, etc. 

 Pressed brick, etc. 

 Paving block, sewer pipe, etc. 

 Roofing tile, draining tile. 



5. Brick clays. 1 /Pressed brick, ornamental brick, 



6. Calcareous shale. / \ Common brick, etc. 



The first division comprises ail elays and shales that contain in con- 

 junction with not less than fifty per cent, of kaolin base little else but 

 finely divided silica. The amounts of the fluxing elements are in all cases 

 small, rarely aggregating as much as five per cent, and generally falling 

 below three per cent. Oxide of iron constitutes much the largest single 

 element of these fluxes. In almost every case the potash is low. Such 

 a division as is suggested here wouM leave out some highly refractory 

 clays, it is true, but the good properties of such would seem to result 

 principally from the silica they contain. 



The second division includes all ordinary clays and shales. They 

 may range in kaolin base from ten to seventy per cent., but they always 

 carry a notable percentage of the fluxing elements. The alkalies gen- 

 erally make two to five per cent., while lime, magnesia and iron add two 

 or three times as much more. Coarse sand and rpck fragments often 

 make a conspicuous part also. These low qualities of the clay more 

 frequently result from a surplus of fluxing element than from a deficiency 

 in kaolin base. 



In the present discussion of these several varieties of deposits, 

 special consideration will be given to those that are found represented in 

 the geological scale of Ohio. Kaolin, china clay, porcelain clay and pipe 

 clay, as they are ordinarily designated and distinguished, do not occur 

 within its boundaries, but all the 6ther divisions named above are found 

 in great abundance and in great variety. Brief descriptions of these 

 several divisions as they occur in Ohio will be given at this point. 



1. Fire Clay.— Between kaolin proper and thepurest fire clay of the 

 state no true line of division can be drawn. In chemical composition 

 they are identical, as seen in the following analysis: 



1. Mineral Point clay. ( IVormley.) 



2. Sciotoville clay. {Lord.) 



Silica. 



Alumina. 



Combined water 



