I have a natural copper nugget found in AZ that looks real similar to these, minus the apparent gold mixed in. Perhaps a copper/gold mixture brought down in the glaciers from Canada. I know there are a lot of natural copper nuggets found in the Midwest from the glacial activity. Chuck Lassiter at midwestprospector.com has found quite a bit of copper. You can contact him via his website and forward your photos. He might be able to tell you what you have, as he is considered a Midwestern gold/gem guru or sorts.
Let us know what you find out, as they are very interesting!