Find the Rock

You are shown a photograph of one particular rock. Somewhere in the environment is that exact rock. Find it.

It begins with about a hundred and twenty stones tipped onto a driveway and ends with a million. In between there is a beach, a riverbed, a quarry, a cave, a snowfield and a museum, and by then you will be measuring things with calipers and arguing with yourself about a white vein.

The game may make finding the rock difficult. It never makes it arbitrary. The stone is there from the moment the case opens, it never moves on its own, it obeys the same rules as everything else in the pile, and it can always be found without asking for help.