Pyrite, etc.,

Here is an odd one\! I collected this one myself, at the Chisel Open Pit Mine, many years ago. It shows a matrix of  pyrrhotite, pyrite, chalcopyrite and chlorite that has spheres/nodules of pyrite embedded in the matrix. The pyrite spheres seem to be in openings slightly bigger than they are and held in place by chlorite crystals! The spheres are composed of small pyrite crystals with chlorite crystals on the outside.  Very unusual! I've always wondered how these nodules  formed!