564 NEW YOKE STATE MUSEUM 



CLASSIFICATION 



As clajs show all gradations from the purest kaolins to the most 

 impure brick clays, it is hard to draw any sharp lines of division 

 between the different kinds. These great divisions can however 

 be made, residual and sedimentary, and to these might be added 

 a third, chemical precipitates. 



Each of these three may include varieties having similar prop- 

 erties and similar uses. 



Seger makes the following divisions: 



1 Yellow burning, containing lime and iron 



2 Bed turning, nonaluminous, ferruginous clays which are free 

 from lime 



3 White and yellow burning, clays low in both iron and lime 



4 White turning, low in iron and high in alumina 



To give a classification based on the uses of the clay is also unsat- 

 isfactory, for some clays may be used for as much as five or six 

 different purposes, either alone or mixed with other clays. 



A rough classification based on their use would be perhaps some- 

 what as follows: 



Brick clays 



Potter's clays 



China clays 



Tire clays 



A good idea of the varied uses of clays may be obtained from the 

 following table compiled by R. T. HilP and added to by the writer. 



Uses 



1 Domestic. Utensils, porcelain ware; china ware; granite or 

 iron-stone ware; yellow ware; rockingham ware; earthenware; ma- 

 jolica; stoves; polishing brick. 



2 Structural. Brick, common, front, pressed, ornamental, hol- 

 low, glazed; adobe; terra cotta; roofing tile; glazed and encaustic 



1 U. S. Geol. surv., Min. res. of U. 8. 1891, p. 475. 



