I'm afraid I don't have much to go on. I was reading another story where the characters were making pottery and suddenly recalled a scene from a book I read... probably about a decade ago. The character in the scene took a special sort of clay out to try and learn something from it. She shaped it into a bowl first, while the narrative talks about the details of pottery, then collapses the bowl and goes into a trance while her clay tells her the future.
I think there were a group of people who could do this (it wasn't only the main character, though she could, too. In fact, I'm mostly certain in the scene I'm thinking of it's not the main character doing the magic). They're trying to learn about an enemy, I think.
Then the clay explodes. I think the character is injured, but they do get some useful information.
If you have any idea what book this is from, I would really like to know. The scene is stuck in my head, but it's not expanding into anything.
Some further details, after reading the guides: The author specifies that the character taps her foot on the bottom of the pottery wheel to start it spinning. I think she does it again, either to keep it going or bump it up a notch, before starting the fortune-telling part of it. I think the first potter was an older woman. The way the pottery is described is very soothing and zen. She talks about the bowl taking shape and growing smoothly under her hands. After making the bowl she sort of... basks in the feel of the bowl under her hands for a moment, then presses in and collapses it from one side, forming a shapeless lump that became the forms for the fortune-telling.