A derivation of Aluminum Oxide, the chemical composition of this Gem is AL2O3. Its exact magnitude is 3.99 to 4.00 and the refractive index is 1.760-1.768 to 1.770-1.779.

Three "special" oxides – aluminum oxide, chromium oxide and silicon dioxide – can actually work to protect metal from further corrosion. So the MIT team set out to explore why this was the case.