Stoneware and low duty refractory clays associated with the Athabasca Oil Sands

Open-pit mining of the Athabasca Oil Sands in the Fort McMurray area removes most of the overburden from basal McMurray Formation clays which have potential for use as stoneware and low heat duty refractories. These clays, interbedded with sands, form the lowest unit in the stratigraphic interval between the base of the mined zone and the underlying Devonian limestone. The clays have good plasticity and working properties, dry reasonably well, have a total drying and firing shrinkage averaging 10 percent, and have absorptions averaging 2.4 percent at the maximum recommended firing temperature. Pyrometric cone equivalent (P.C.E.) varies from 10 to 23 with 16 as the average from 70 samples. Chemical and mineralogical data suggest that a high content of potassium associated with abundant illite may be a significant factor in control of sample refractoriness. Fired colours are shades of yellow, brown, and grey. Thorough evaluation of these basal clays, to outline the most refractory portions of a deposit, would be necessary prior to extraction for stoneware and low duty refractory uses.

Clays from within the mined zone have characteristics similar to those of the basal clays and similar uses can be suggested for them. However, the clay material rejected as "oversize" from the feed material for the oil extraction plant because it remains in large cohesive chunks after mining generally contains enough oil sand, in variable amounts, to preclude the use of the clay for ceramic purposes. The intraformational clays that are subjected to the primary extraction process must be concentrated from the waste stream and they remain contaminated with a small amount of oil. Firing shrinkage is high and bars curl at high temperatures, but the P.C.E. of 23 and the easily accessible unlimited supply of this material suggests that further research to evaluate these clays might be worthwhile.