...a piece of petrified wood. I picked mine up* at the Painted Desert/Petrified forest when there on vacation.
*I purchased mine at a gift store within the national park, I did not pluck it from the park. That would be highly disrespectful and illegal.
What Is It? is a feature you can add to your classroom. Once a month, or thereabouts, put out something new and ask students to try to identify it. If they figure it out correctly, give them extra credit, a prize, a high five or bragging rights!