I just call it how I see it, bit that doesn't mean I'm correct.
Here's a VERY LARGE
version of the photo to see the clay up close.
I called it pin zi ni because there is quite obviously a lot of yellow sands blended into the lighter purple clay, as well as those iron dots too. My most specific label I could apply to this clay would be "duanni tiao sha" because of the high yellow sand content mixed in. Here is a very large closeup
of another pot I would describe as duanni tiao sha, but with a finer texture.
"Duanni pu sha" is different- that's when they push flecks of duanni in to the outer surface of the clay for decorative reasons (see here
). A lot of modern zi ni has some yellow sand blended in which you can see most obviously under the lid's skirt or where the top of the pot was ground down (like this pot
), but I wouldn't call it tiao sha because there isn't enough yellow sand to fit that category in my opinion. Where to draw the line between duanni tiao sha and regular zini with a bit of yellow sand is certainly up for debate... but let's not.