It tends to form in cubes. Striking it with steel produces a spark. Best Field Indicators are crystal habit, hardness, streak, luster and brittleness. Color is brassy yellow. Luster is metallic.
Crystals are opaque.
Good interpenetration twins called iron crosses are rare. Found commonly in nodules. Also massive, reniform and replaces other minerals and fossils forming pseudomorphs or copies. Cleavage is very indistinct. Fracture is conchoidal.