THE NONMETALLIC MINERALS. 



329 



could be made to far exceed the entire limits of the present volume. 

 The names fat and lean clays are workmen's terms for clays relatively 

 pure and plastic or carrying a large amount of mechanical admixtures, 

 such as quartz sand. 



In the Kaolin and China Clays are included a series of clays used 

 in the manufacture of the finer grades of porcelain and china ware 

 and which consist in large proportion of the material kaolin, the name 

 being derived from the Chinese locality Kaoling, from whence have 

 for ages been obtained the materials for the highest grades of Chinese 

 porcelain. 



According to Richthofen, 1 however, the material from which the 

 porcelain of King-te-chin is made is not kaolin at all, but a hard 

 greenish rock having somewhat the appearance of jade and which 

 occurs intercalated between beds of clay slate. He says: 



This rock is reduced, by stamping, to a white powder, of which the finest portion 

 is ingeniously and repeatedly separated. This is then moulded into small bricks. 

 The Chinese distinguish chiefly two kinds of this material. Either of them is sold 

 in King-te-chin in the shape of bricks, and as either is a white earth, they offer 

 no visible differences. They are made at different places, in the manner described, 

 by pounding hard rock, but the aspect of the rock is nearly alike in both cases. For 

 one of these two kinds of material, the place Kaoling ("high ridge") was in ancient 

 times in high repute; and, though it has lost its prestige since centuries, the Chinese 

 still designate by the name " Kao-ling," the kind of earth which was formerly derived 

 from there, but is now prepared in other places. The application of the name by 

 Berzelius, to porcelain earth was made on the erroneous supposition, that the white 

 earth which he received from a member of one of the embassies (I think, Lord 

 Amherst) occurred naturally in this state. The second kind of material bears the 

 name Pe-tun-tse ( ' ' white clay " ) . 



The following analyses will serve to show the average composition 

 of (I) the natural material from King-te-Chin, such as is used in the 

 manufacture of the finest porcelain; (II) that from the same locality 

 used in the so-called blue Canton ware; (HI) that of the English Cor- 

 nish or Cornwall stone; (IV) washed kaolin from St. Yrieux, France, 

 and (V) washed kaolin from Hockessin, Delaware. 2 



1 American Journal of Science, 1871, p. 180. 



2 Analyses I and II by J. E. Whitfield, Bulletin 27, U. S. Geological Survey; III 

 from Langenbeck's Chemistry of Pottery; IV from Zirkel's Lehrbuch der Petrog- 

 raphy, III, p. 758, and V by George Steiger, U. S. Geological Survey. 



