Corundum

Corundum is the mineral of aluminum oxide (alumina) crystallized in a hard form. Ruby and sapphire are forms of corundum. Artificial Corundum could be made on the moon by purifying aluminum oxide, melting it, and recrystallizing it. Corundum is produced artificially by various growth methods from very pure molten alumina. at 2100C. It is useful as grit for abrasive machining of cast basalt, iron and steel Corundum can have a hardness of 9 Mohs.

Corundum doped with iron or titanium with produces blue sapphires than can be used in lasers and optics. Corundum doped with chromium produces red rubies that are also used in optics and lasers.

Corundum cut from large boules (a single cristal grown from the molten alumina bath) create exceptionally strong and transparent windows for instrumentation.