I have a very nice teapot bought and sent to me by a friend stationed at that time in Beijing. It is extremely heavy and I am quite sure it is made of cast iron. The inside appears to be of some highly glazed black material. I can find nothing on the 'Net about cast iron teapots so would appreciate any information members are able to offer. Thanks
Usually experience tea drinkers use cast iron kettle to boil water, which keeps the temperature well and accordingly to some studies, the cast iron kettle water may release some iron as well. However, cast teapot has glaze which would trap the temperature and would cook the leaves. This would not allow the leaves to stay fresh and also, since it is glazed, the teapot could not release the iron. Hence, I would not recommend using it for making tea.