OK. Bob and others are correct. After extensive scientific testing and consulting with four highly skilled technicians and my shop foreman, we have concluded that it is, indeed, plastic or some form of composite. I trimmed the sharp edge off the base of the impeller on opposite sides enough to remove any "coating" if there was any and checked for continuity and it has none. One tech said it tastes like plastic (As I said, they're highly skilled) and another said it did not stick to his aluminum magnet.
I'll give it this, it sure is some hard stuff. I'm going to see if I can get someone at Concentric and see if they can tell me what it is.