MESOZOIC CLAYS AND SANDS 



43 



This clay could be used also for the manufacture of stoneware 

 pottery, but for this purpose it would have to be washed and screened 

 in order to free it from coarse grit. 



The white clay is somewhat more refractory than the mottled 

 clay, and when washed would probably be suitable for the manu- 

 facture of white, floor and wall tile and for sanitary ware. 



Chemical Analyses of the Various Clays 



I. White clay, Missinaibi river. Analyst, M. F. Connor. 

 II. Mottled clay, Missinaibi river. Analyst, A. Sadler. 



III. Mottled clay, Wabiskagami river. Ontario Bureau of Mines. 



IV. White clay, Mattagami river. Ontario Bureau of Mines. 



The almost complete absence of lime, magnesia and alkalies in 

 these clays shows that they are very different materials from the 

 Glacial or inter-Glacial clays, in which the sum of these active fluxes 

 ranges from 15 to 30 per cent., and makes them easily fusible. 



No. IV is an exceptionally high grade clay as regards refractori- 

 ness, as it stands as high a temperature as English china clay before 

 deforming, and is the only example of a No. 1 fire-clay so far found in 

 Canada. 



Origin of Clays 



The Cretaceous clays and sands, found at intervals near the 

 margin of the great pre-Cambrian area in Canada, are derived from 

 the weathering and decay of the older crystalline rocks. The clays 

 have been derived chiefly through superficial weathering and kaolin- 

 ization of the feldspar in these rocks, while the residual quartz has 

 gone to the formation of the sands. A climate favourable to weather- 

 ing and leaching, a long period of stability of the region with regard 



