corundum, anorthite and biotite. A crystallo-chemical enigma, it is one of the few rock-forming minerals with unknown crystal structure.

Crystal field theory makes predictions about how a transition metal ion’s structure is affected by the other atoms surrounding it. Rubies are mainly made up of the mineral corundum, which is ...

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 ...