Out near the northern tip of Michigan’s Upper Peninsula, on the shore of Lake Superior, is the village of Copper Harbor. There was a copper mine in the hills above that mined a deposit of pure metallic native copper. The story goes that they had a helluva time extracting the copper mass. Explosives would deform the metal a bit, but it would not break up for removal. There was very little rock interspersed with the heavy copper metal veins.
These two were once one piece. I got this back in the 60s when I spent summers in the UP with family. I tried to break the thin connecting strip between the two chunks, but it would only bend. I had to resort to a hack saw to cut them apart. You can see the brown aged copper where they separated along the bottom edges. This nugget is solid metal all thru and weighs about 5 lbs.