KAOLIN. CHIN. Porcelain clay.
Kau-ling-t'u, . . Cols. I Kiri-matti, . . Peh-ngool, . . . . „ This is the aluminous ingredient of Chinese porcelain, named after a bill near Kin-teli-chin, in the Kiang-si pottery district. It is a silicate of alumina. Petun-tsze is the silicious element in Chinese ware.
For a long period it was erroneously supposed that the fine clay necessary for the production of good porcelain, consisting of silica and alumina in variable proportions, and called by the Chinese kaolin, was peculiar to their land, and that conse quently no country in Europe could hope to attain eminence in this manufacture. But kaolin abounds in Ceylon, and in the 15th century was exported to China. Porcelain clay is very abundant in S. and E. Asia, produced by the decomposition of felspar. As it occurs in Ceylon, an analysis in 1867 showed pure kaolin 70, silica 26, molybdena and iron oxide 4 = 100. Kaolin is procurable in great abundance in Southern India.
In a report on the geology of the North Arcot district, Mr. Bruce :Foote writes : The highly felspathic varieties of the granite gneiss are occa sionally so greatly decomposed as to appear to offer sources for the collection of kaolin or China clay. But none of the North Arcot localities show rocks sufficiently rich in decomposed felspar to be of much importance. A very serious disadvantage
is the difficulty of a suitable water supply. To insure the preparation of kaolin of good colour, which alone commands a high price, a very largo supply of perfectly limpid water is a sine qua non. And in a dry climate like that of the Carnatie, this want could only be met by the construction of special reservoirs of large size, in which the water could be allowed to stand for many months after the rainy season, till all the suspended particles of ferruginous clay had settled, and the water itself had become perfectly limpid. If the great cost of providing such supplies of limpid water free from saline matter in an eminently dry country be taken into consideration, together with the fact that the kaoliniferous decomposed rock occurs in greatly smaller quantity, and is generally much less free from ferruginous staining, due to the filtration through the almost universally overlying. red soil, the conclusion seems inevitable that the prospects of establishing profitable China clay works in North Arcot are not very promising.'