Size  4cm x 2cm
A solid piece of copper metal, showing cubic crystals in the main cavity as shown in the photos. There is also sprays of clear needly crystals in the cavities with the copper crystals as well, these were only noticed recently and have not been identified. The speciman was from an old collection with not much information on a location, just america, which doesn't narrow it down very much.
I myself, feel that this piece has come from a copper refinery/smelter somewhere, but I am not sure, maybe someone else will know and identify the clear crystals.