170 ECONOMIC GEOLOGY 
which when present in mass forms china-clay. It is so 
named from its use in China for making porcelain—a word 
invented by the Portuguese in support of the assertion that 
the material was made from the shells of a cowrie named 
Porcellano. One important occurrence of china-clay is at 
Kauling or “the high ridge ” near Jao-chow Fu, S. of the 
Yangtze-kiang and E. of Lake Poyang; Berzelius named 
china-clay Kaolin under the impression that it was the raw 
material of this ridge. Kaolinite—the crystalline form-is 
only one constituent, and is isolated by washing ; in Cornwall 
it forms on an average about a quarter of the mass. The 
careful washing for the finer qualities of Chinese porcelain 
Fic. 50.—A CHINA-CLAY Mass IN CorRNwALL., 
The dotted area represents the china-clay developed in the granite (shown 
by short lines); 4, a band containing biotite; Z, zircon crystals in 
the overlying soil ; none were found in the china-clay. Parallel lines, 
slate, kaolinized near the contact with the granite, Dark lines, 
tourmaline veins. 
has given rise to the statement that one man begins to wash 
the clay and his grandson makes the pot. 
China-clay in Cornwall and Devon (Fig. 50) occurs in deep 
blocks and pipe-like masses in granite, and it consists chiefly 
of quartz, white mica, kaolinite, tourmaline, and topaz. 
The quartz is in rounded corroded grains which from their 
shape and size have been compared to mulberries. The 
washed residue consists of a pure white clay composed of 
minute flakes of white mica and kaolinite. ~The kaolinite 
crystallizes in hexagonal scales which have a highly developed 
basal cleavage, and are very similar to muscovite mica. 
The tourmaline is of the black variety, schorl, and occurs in 
scattered crystals or in veins which may extend into the 
granite and are then bordered by china-clay. Small crystals 
of topaz are common ; flakes of biotite remain where it was