THE CHINA CLAY INDUSTRY OF CORNWALL AND DEVON. 13P 
to the Royal Geological Society of Cornwall in 1876, fairly 
represent the composition of average specimens of the materials 
described above. 
China 
Clay 
China 
Stone 
Mica Clay 
Coarse 
Mica 
Sand 
Silica .... 
45-40 
71-66 
46-70 
56-41 
81-50 
Alumina .... 
40-30 
18-79 
35-20 
29.60 
13-40 
Lime .... 
trace 
1-70 
trace 
— 
— 
Magnesia .... 
trace 
0-35 
— 
— 
— 
Peroxide of iron 
0-20 
trace 
1-90 
2-72 
2-50 
Alkalies, insoluble and loss 
0-60 
6-60* 
4-66 
4-37 
0-10 
Fluorine .... 
trace 
0-14 
trace 
trace 
trace 
Oxide of manganese . 
— 
trace 
— 
trace 
— 
Water .... 
13-50 
0-91 
11-54 
6-90 
2-50 
100-00 
100-15 
100-00 
100-00 
100-00 
All the older writers speak of “Talc,” “Talcose granite,” 
“ Protogine,” &c., as being abundant in Cornwall and elsewhere. 
Even Mr. J. A. Phillips, writing in 1875, says: “In some 
districts mica is replaced by a talc-like mineral, and the granite 
rock itself passes into protogine.” What there may be elsewhere 
I am unable to say, but there is certainly nothing of the kind 
known at present in Cornwall. From the whole of the granite 
! districts of Cornwall and Devon talc seems to be entirely absent, 
and magnesia generally is an extremely scarce substance. 
The number of china clay works at present in operation in 
Cornwall and West Devon is little short of 200, and of course 
the conditions of working vary considerably in different localities 
and under different conditions. In some, a little washing only 
is done during the winter months by means of a small natural 
stream of water, the total annual produce being only a few 
hundred tons ; in others, valuable machinery and extensive 
buildings enable the proprietors to turn out nine or ten thousand 
tons in the same time ; but in the main the description given 
above as fairly describes the occurrence and preparation of china 
clay and china stone as is possible within the limits of such an 
article as the present. 
The trade at present is much depressed — mainly, I believe, 
owing to the slackness on the part of those (potters, paper- 
makers, bleachers, and others) who use clay ; but partly, perhaps, 
owing to the over-production of a few years since. In consequence 
of this the prices have fallen more than 30 per cent, during the 
last five years, and the quantities produced have also shown a 
Chiefly potash. 
