I'm going to go against the grain and state chalcopyrite instead of pyrite. Both have similar composition. Pyrite (fool's gold) is mostly crystaline structure, often cubic, even massive. Chalcopyrite has enough copper in it to look slightly duller with smaller crystaline structure (at least in my area).
One way to tell the difference will be a streak-plate test: scratch the stone on an unglazed tile surface, and take a look at the color left. Most of the pyrites will leave a colorful streak (look 'em up online). An iron-nickel meteorite will leave a different color streak, if at all. Most are so hard to leave little streak: like trying to get a streak from a stainless steel fork, spoon or knife.