I found a rock that looks volcanic in my yard i live in missouri however

i was digging a spot for my greenhouse and hit a couple stones combined weight maybe 3lbs looks like lava outside but where it is broke it looks like black glass i guess my real question is can anyone help identify these rocks i have pictures

Where are your pictures? If it looks like black glass, it might be obsidian. Does it have concoidal fracture?

It is probably slag which a byproduct of iron refining.

http://pages.ees.ufl.edu/townsend/files/…
http://media.giantbomb.com/uploads/13/13…
http://i00.i.aliimg.com/photo/v0/1032525…