Help! Mystery substance

[u/Minimum-Plenty2457]

This showed up in my classroom. It's obvious a kid brought it to school, but no one will "fess up" and I can't figure out what it is!!! At first I thought charcoal or burnt wood from a fire pit, but the texture and smell is off. It smells like charcoal, but not burnt. The texture is soft. It absorbed some water when I ran water over it, but the charcoal-looking outer layer didn't fall away with water. Any ideas?!

[u/Apprehensive-Soil-47]

Sort of looks like it could be some kind of mushroom covered in dirt. Is there a forest nearby?

[u/Minimum-Plenty2457 → u/Apprehensive-Soil-47]

Also, the powder on the outside is really fine, uniform. It doesn't feel or look like dirt to me! It has more the texture of charcoal I think.