Gahnite, ZnAl2O4, is a rare mineral belonging to the spinel group. It forms octahedral crystals which may be green, blue, yellow, brown or grey. It occurs in Falun, Sweden where it is found in pegmatites and skarns, contact metamorphic rocks. Other occurrences include Charlemont, Massachusetts; Spruce Pine, North Carolina; White Picacho district, Arizona; Topsham, Maine; and Franklin, New Jersey in the United States. It was named after the Swedish chemist, Johan Gottlieb Gahn (1745-1818) the discoverer of the element manganese. It is sometimes called zinc spinel.