What are these very heavy blocks found on my family's property?
They are iron ( unlikely steel at that age ) identified by the density match to iron. The reddish color that looks like granite is rust on a pitted surface. Pig iron ( high carbon and silicon ) or wrought iron ( more or less pure iron ). An unusual shape for either as far as I know. My guess is that they are raw material intended to be made into something. A real historian would be necessary for a comprehensive identification. I have never seen a shape like that except a modern ( after 1975 ) continuous caster could cast 5 X 4.5 inch square strand.