Teacher: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Category: EVERYBODY TALKS ABOUT IT... 
Clue: In the winter of 1971-72, a record 1,122 inches of snow fell at Rainier Paradise Ranger Station in this state
Solution: washington
Reason: Rainier Paradise Ranger Station is located in the Mount Rainier National Park, which is located south of Seattle in the state of Washington.

Now, solve this instance: Category: ROCKS & MINERALS 
Clue: Kaolin, a pure type of this potter's material, is formed when feldspar decomposes
Student:
clay