Cut a small 3" dia branch or so...if it has dark heartwood its black walnut...pat might be onto something,but the bark seems a lil off for pecan/hickory...but bark in pics and even in person can be vary misleading and deceiving,and not a very good indicator all the time...wish I could see it all in person,cus that's the easiest way to id it for me ..and yeah..any old nuts or hulls laying around?