I dumped some corn cob in with my walnut because I had a little new left and didn't intend to buy more but didn't want to waste it. It seems to work pretty good. I really had no idea it was bad to mix them. I know in your case it was unintentional but I bet it would still work pretty good. I do have more dust now that I think about it though. Maybe the walnut in grinding up the corn cob?