Difference between corundum and high-alumina

1. The main ingredient of 90 corundum brick is corundum and a small amount of soil in Suzhou, mullite.
2. The main ingredient of alumina bricks is high bauxite, corundum mullite and some sand.
3. The difference between them lies in how much alumina content, alumina content higher than 48% of alumino silicate refractory products 
4. Al2O3 content higher than 90%, referred corundum brick.
5. Hardness can tell the difference. To cut with a hacksaw, corundum is the hardest, followed by high aluminum and most soft clay qualitative