I wasn't sure exactly what category to out this under but we moved into a house and I believe we have a walnut tree in the yard. There are some green balls but a bunch of white shelled one's too. I cracked one open and it looked like a walnut inside. I can't seem to find any pictures of the white shelled one's we found. Most sites say you have to keep the green back first buy we have a bunch already out. Are these actually walnuts and if so what kind?