Tourists tried and failed to light fossilized wood on fire, which also happens to be illegal.

"I was working in Petrified Forest National Park as a researcher... I watched two tourists pick up pieces of petrified wood (so, rocks) and try their hardest to light them on fire. This is actually illegal, as was their decision to take the pieces of petrified wood home with them when they finally decided that they wouldn't burn. I waited until they left and then called them in to the law enforcement. They were stopped at the gate and their car was searched."