ncuke, I run across those all the time in my creek and they hook me almost every time especially if they have creek patina on them. If they have a curve to them I bring them up to wash just to make sure. Yesterday I thought I had one but decided to clean it up and was soaking it. When I took it out of the soak and it felt like pottery and I took an even closer look and it was, needless to say I was very glad I hadn't tossed it on the bank or back in the creek like I usually do. So keep looking especially if you have found any shards or other artifacts where you found this piece, it will pay off in the long run.