The colors of rubies and emeralds are so striking that they define shades of red and green—ruby red and emerald green. But ...

Aluminum oxide (Al 2 O 3), also known as alumina, corundum ... On the surface, however, the structure deviates from that inside the crystal. The strongly insulating nature of alumina has hindered ...

More than 4,000 naturally occurring minerals—inorganic solids that have a characteristic chemical composition and specific crystal structure ... of a mineral called corundum, comprised of ...