Chalk

Chalk is a powdery crystalline substance that comes in the form of a pencil, which is used for making pictures and for writing on blackboards and slates. Chalk can come in a variety of different colors.

In the EMPATH: The Luckiest Smurf story series, Brainy uses chalk when presenting his lessons to the Smurflings in the Smurf Village Schoolhouse. Wild Smurf upon his first visit to the Smurf Village thought that chalk looked like food and tried to eat one, only to not like the taste.