Sapphire has a density of 3.95–4.03 gcm-3. \(Al_2O_3\) has a density of 3.987gcm-3.
It is likely that in the formation of sapphire, \(Al_2O_3\) is stripped of its other proton layer with twelve paired orbits (three paired orbits from two \(Al\) and nine paired orbits from three \(O\) ), in a barrage of \(T^{-}\) particles. This way density increases. The subsequent \((T^{+},\,T^{-})\) paired orbits bond and form a crystal lattice. Given that the twelve paired orbits is the maximum number of orbits possible with equal angle (63.4o) in 3D space, the lattice formed as the orbits bond is also the maximum variety possible.
Goodnight.
