corundum

The Gucci x Oura Ring is made out of “black synthetic corundum” detailed with a braided border and an 18-karat gold Gucci G. It weighs four grams, and the band measures 0.3 inches thick.

If the quartz can’t scratch the specimen, it might be beryl or corundum, which are harder than quartz.

These include substrates of strontium titanate, aluminium oxide and magnesium aluminate, which have perovskite, corundum and spinel crystal structures, respectively.

A. Both rubies and sapphires are mostly the same clear mineral: aluminum oxide, in a crystalline form called corundum.

Recent research suggests that traces of silicon, too, play a role in determining the color of corundum, but its exact role has not been determined.