Don't forget to think about the rays.
I'm sticking with 'Black walnut', based on weight, availability...but have a lower % of confidence.
Color wise matches well to "blonde walnut' finishes. Black walnut has a range of natural color, from tan to rich brown to a dark, almost coffee. Often younger trees have a lighter colored heartwood. Many in the
Juglans genus have a chambered pith, looks like you have plenty of pith to investigate to confirm at least family.
I looked through my small number of walnut species samples. I found one Claro walnut sample expressing rays in small proportion and one Persian walnut expressing rays the entire 6" length of the sample. So Larry could also have a match. My Persian sample had a very dark heart and white sapwood. The rays were seen in the sapwood. For the wood in this post, I think the rays are expressed to their maximum as the grain is not straight, and curves as well as rises and descends, showing the rays in the longest likely view. I think the tree started under some sorts of stress, boxed pith and early growth rings for the one piece. The chatoyance hints possible interlocking grain in the heavy ray flecked piece, or an allusion of light as the grain curves, rises and descends.
Need to bisect the pith. You can cut just above the pith and use a sharp jointer and plane down a few 32nds at a time and check each pass to see if you have a chambered pith, as seen in the twig below.