Hercynite is a spinel with the formula FeAl2O4.
It occurs in high-grade metamorphosed iron rich argillaceous and ultramafic. Due to its hardness it also is found in placers
It was first described in 1847 and its name originates from the Latin name for the Harz
Hercynite is a spinel of regular symmetry and normal cation distribution, but some disorder occurs in its structure. It consists of ferrous (Fe2+) ions and aluminium ions (Al3+), however some ferric ions (Fe3+) may be located in the structure of hercynite.