What is the difference between alumina and white corundum?

Alumina is a high hardness compound with a melting point of 2054 degrees Celsius and a boiling point of 2980 degrees Celsius. It is often used to make refractory materials. The main component of corundum is α-alumina, which is second only to diamond in hardness. Ruby and sapphire are high-quality corundum containing a small amount of different metal oxides. Ruby is generally red because it contains a small amount of chromium, and sapphire is blue because it contains a small amount of iron and titanium. To

Corundum is a kind of alumina crystal with good crystallization, and the relationship between the two is similar to the relationship between crystal and quartz powder