I bought a tetsubin iron cast pot from an online vendor about a month ago. After about a week I noticed small black granules in my teacup that I presumed where tea sediment. A few days after that though a whole piece of black coating from inside the barrel of the spout came undone. I called the vendor who was willing to exchange the pot saying it had never happened before and they sell hundreds of them every year. I got the new one in the mail a few days later and I thought my problems were behind me but yesterday the same thing happened, a big piece of the black coating inside the spout dislodged itself into my cup. I don't use the teapot on direct heat source actually the water I include in the pot is not even boiling when I pour it from the kettle. This particular teapot is made in China. Has anyone had a similar experience?