A raw material with a high content of aluminum oxide has the following
composition, in weight-percent, based on dry weight:
1
Al.sub.2O.sub.3 50-80%
MgO 2-15%
SiO2 1-15%
CaO 0.5-20%
Fe.sub.2O.sub.3 0.5-2%
Na.sub.2O 0.5-2%
Al (metallic) 0.1-2%
AlN 0.1-1%
K.sub.2O 0.1-1.5%
F 0.1-2%
Cl 0.1-0.8%
balance in
total, not to exceed 5%
loss on ignition, not to exceed 15%
The main mineral constituents of the raw material are, in weight-percent
2
aluminum hydroxide 20-60%
corundum
.alpha.-Al.sub.2O.sub.3 10-40%
spinel MgAl.sub.2O.sub.4 5-40%
Specifically, the aluminum hydroxide is present as aluminum mono-hydroxide
Al.sub.2O.sub.3.H.sub.2O and aluminum tri-hydroxide
Al.sub.2O.sub.3.3H.sub.2O in a weight ratio exceeding 0.25.
