There are a variety of ores that when cut show the patterning you have there, and meteorites as well though I rule that out for your specimen. One can see a large number of crystal boundaries and by the distortion your stone has been altered by high pressure much like metamorphic rock. As to its composition check for magnetism, try a streak test, hardness test, specific gravity test and if you can find someone with an XRF reader it would help. Off the cuff I'd guess its a mixture of iron sulfides much like pyrite.