This would be a great activity to begin a discussion over what exactly is a fossil and how do they occur. If possible, it would benefit the student if you could provide examples of the different ways fossils are preserved.
Petrified wood is an example of permineralization.
Plant fossils are preserved by a process called compressions, and in Ohio, common replacement minerals are pyrite and silicia. The site provides background information on the different ways fossils are preserved and the procedure to make fossil molds and casts. First define what a fossil is and where fossils are most likely to occur. Pass around the hand samples that represent the different processes of permineralization, compressions, and replacement. Explain each process and hold a class discussion over the events that need to occur before fossilization can begin to take place.