5o 



INTRODUCTION. 



There are no high-elass ceramic industries in Canada 

 using Canadian clays, because there are no kaolin deposits 

 of worth in Canada. Pleistocene glaciation removed all 

 products of rock decay, and therefore all deposits of residual 

 clay, and left only a mixed glacial drift. In some places 

 this has been more or less sorted, so that a clay-like material 

 containing a large percentage of rock flour is found, and 

 this is used for the manufacture of ordinary building-brick, 

 field tile, or common pottery. These impure clays in the 

 fresh and unaltered state are high in calcium carbonate, 

 varying from 13 per cent, to 27 per cent. The iron oxides 

 run about 7 per cent. In burning these clays the iron is 

 prevented from burning to the ferric oxide, but forms in- 

 stead ferrous carbonates and silicates, which give the buff 

 to cream colors found in these products. There is an un- 

 limited supply of this clay in Canada, but it is of a poor 

 grade and yields only the commonest products. 



In flat areas, or in more or less hollow places, where 

 weathering has taken place, and where the products have 

 had little chance to be removed, we find that the meteroic 

 waters have leached out the calcium carbonate from the 

 upper two to eight feet of our glacial clays. This has re- 

 duced the calcium carbonate to as low as 6 per cent, in most 

 cases, but since iron oxide is insoluble it remains the same 

 as in the glacial clay. On burning this weathered clay, the 

 iron oxide is now able to change to the ferric condition, and 

 yields as a result the red products with which all are 

 familiar. 



Since this red-burning clay is confined to the weathered 

 top of the glacial clay and to interglacial clay, we can see 

 that the supply is limited. Beyond the change in color, the 

 other qualities of the burnt product are not improved. 



All higher grade products, including pressed-brick, terra- 

 cotta sewer-pipe, paving-brick, etc., are made in Canada 

 from shales of the Paleozoic series. Three of these are 

 used so far in Canada, namely, the Utica, Lorraine and 

 Medina. The first of these is used in the vicinity of Mont- 

 real, but has not yet been used in Ontario. The latter two 

 are used in the vicinity of Toronto. 



