Aluminous brick made by the Semiluks Refractories Plant containing 60% Al2O3 sinters intensely, with sharp changes in properties and reductions in refractoriness from 1810 to 1750°C when used at temperatures of 1500–1600°C. The least-change zone and working zone of the refractory consist mainly of mullite and glassy substance. The amount of mullite increases in the direction from the least-change to the working zone. It is necessary to use high alumina refractories with a higher content of Al2O3 (70–72%), preferably with increased density, in order to increase the life of the linings in hot air stoves.