betta wrote:Does anyone know how to differentiate mixed zhuni from pure zhuni?
That is quite a difficult question. If the teapot is cheap, it is definitively not good zhuni. But if it is expensive it doesn't mean it is good zhuni...
Don't be too focused on the teapot, be more focused on the tea.
For most teas, basic teapot (porcelain, glass) or kyuusu is all what you need.
If you are on Puer, buy a decent teapot (you should anyway need a zhuni, zisha or duani only for Puer and oolongs although you can brew them in a gaiwan): small capacity (10 to 20 cl) and good heat keeping. I bought mine for about 50€ (75 US$) from a Taiwanese vendor because I liked the teas he sells ans also because I tend to think that food related item safety is stricter in Taiwan than in China.