Habit: Typically dark to sea green but also colorless, white, blue, pink, greenish yellow or black. Crystals rod-like to fibrous, with long prisms. White streak.
Environment: Occurs in silicon-poor, magnesium- and aluminum-rich gneisses, often associated with cordierite, sapphirine, corundum and sillimanite.
Etymology: Named in honor of the Danish geologist Andreas Nikolaus Kornerup (1857-83).