Aligator or Dinosaur Fossil skin type rock
I agree with commentator @John, this is a fossil coral.  The coral animal (the polyp) builds a column, and as it ages it closes off the bottom and extends the upper lip.  In some of the views you see the column structure.  In others you see the arrangement of polyps.  It looks like the cells of the coral are filled in with calcite, which probably made the fossil harder than the surrounding rock.  When the rock weathered the fossil coral broke apart.  It looks like this piece is a rounded pebble from a stream bed.  Or possibly the coral broke up and was rounded by wave action.

Compare this picture http://www.fossilmuseum.net/fossil-art/cnidaria/tabulatecorals.jpg