Manuports

The Makanpansgat Cobble might be the earliest known "cool rock." Credit: Brett Eloff If you look around your bedroom, or in the door pocket of your car, you may have a cool shell you've found and kept. Maybe it's a nice pinky-orange, or has a perfect little hole so that one day you could make a necklace. If you've ever picked up such a shell, a good…