Ok my friend gave me this rock he found within a nother rock,it is shiny silver, and very heavy, it cuts glass

ok this rock was found within another rock. it is silver and has a few little holes in it. it cuts glass.when he took it out of the other rock it was like a vain in it. nothing would break it including sledge hammer or a diamond cutter its weird. I even could cut into a canadian quarter, but then there was some stuff that came off the rock, and it kinda like silver dust or lead. but i dunno what this weird rock is? i find it neat any ideas?