I think the piece you split is Black Walnut, but one that grew fast leaving a wide white sapwood ring around the narrow dark hearthwood. most of the Black Walnut I have cut has more dark and less white, but the same general look and same bark as yours. I still say the stuff in the pic on the right looks like Norway Maple. Norway Maple grown as a shade tends to be very full of knots, crotches, Ys, and other tough pieces. I have picked up loads that were almost all tough pieces and only a few easy ones.
