I’ve been poking around some geologists’ blogs and found this terrific post about a mystery rock. Diego wrote to Evelyn Mervine about a rock he had found. He wanted to know if she could tell him what kind of rock it is. The great thing about her response is the list of questions that she would ask of the rock.

Mystery Rock. What are those markings?

Read the post and the comments to see how geologists think as they solve puzzles like this.