I'm a little curious whether or not you using a yixing teapot would work for black tea. If that's the case, what should I look for? Should it be a compressed shape? Should it be Black Clay? I usually drink keemun and lapsang souchang, but I'm also interested in Yunnan Gold
I've got one for qimen and one for darjeeling, I'm thinking one for Assam next. The potters of yixing use their famous teapots to brew yixing black/red tea. You can't really argue if they're doing it.
I wouldn't think shape would matter too much. I head towards thicker and darker clay as I figure a light clay will end up dark anyway and due to the temperatures that black/red can endure thick clay seems a good choice.