My "solid part" was identified as slag. It had a weight to it. It was non-magnetic. Mine was about 2x2 in. with a small "drip"? Also mine had one smooth side that I thought had impacted the earth..Prof. told me it only fell feet not miles...IDKSlag?! The hollow part has kind of a slag feel but the other half feels solid
Your first photo with the quarter for size, it looks like the underside of a claw with the growth groove.