[keele] MESOZOIC clays AND SANDS 39 



Mclnnes,' are made up principally of soft, white sandstone and thin 

 lignite seams, and the clay content appears to be very small. 



The most extensive clay beds of Lower Cretaceous age occur in 

 northern Alberta on Athabaska river and its tributaries north of Fort 

 McMurray.2 



The Athabaska clays overlie Devonian limestone and were 

 deposited near the western margin of the Pre-Cambrian area, where 

 they are associated with incoherent white sands which have become 

 impregnated with bitumen and hence are often referred to as tar 

 sands. Although many of the clay beds in this region yield refractory 

 materials of fairly high grade none of them was found to equal the 

 best of the Mattagami clays. 



The exact position of these sediments in the Cretaceous is only 

 approximately known at present, but it seems probable that the 

 Manitoba and Saskatchewan beds are more recent than the Athabaska 

 and northern Ontario series, the latter being probably the oldest of all. 



Physical Properties and Chemical Composition of Clays 



AND Sands 



The clays contained in the Cretaceous deposits in northern 

 Ontario are of high grade and of a class quite rare in Canada. If 

 they were situated close to transportation and easily mined they 

 would have great industrial value owing to their good working qualities 

 and their refractoriness. Samples taken from the borings on Matta- 

 gami river were tested by the writer in the laboratories of the Mines 

 Branch, with the following results 



Mattagami River 



The clays are smooth and free from coarse grit with good plasticity 

 and working qualities. Only sample No. 10 contained a quantity 

 of coarse quartz grains which had to be separated by washing. The 

 contrast in colour and texture of these materials to the ordinary 

 glacial clays of the region is very striking. 



The following table shows the character of the various clays 

 when burned in a commercial stoneware kiln to cone 7. 



A portion of each sample was dipped in Albany slip glaze before 

 firing. The glaze was found to be fully matured when the samples 

 were drawn from the kiln. 



1 Geol. Surv. Can., Mem. 30, p. 65. 



- Mines Branch, Ottawa, Bull. No. 10, " Notes on Clay Deposits near McMurray, 

 Alberta." 



