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.
Streak is greenish black. Brittle, striations on cubic faces caused by crossing of pyritohedron with cube. Pyrite unlike gold is not malleable. Associated Minerals are quartz , calcite , gold , sphalerite , galena , fluorite and many other minerals. Pyrite is so common it may be quicker to name the unassociated minerals.