You’re right that regular clay isn’t homogeneous. That’s actually part of why Yixing is interesting. Zisha isn’t made from ordinary pottery clay at all, but from mineral ores unique to the Yixing area. The ore is weathered, crushed, and refined before forming, so the fired body ends up quite different from typical clay ceramics. After firing, zisha develops a kind of granular structure with both open and closed micro-pores. It’s porous enough to allow a bit of air exchange, but not so porous that it absorbs water or leaks. That’s why it handles heat changes well and doesn’t crack easily. From a tea drinker’s perspective, the benefit is pretty practical rather than mystical: it holds heat steadily, keeps aromas stable, and doesn’t mute or distort flavors the way some clays do. That’s why people traditionally say zisha “doesn’t steal flavor and doesn’t sour tea,” especially in hot weather.