Small pieces of noble shungite. Used in Russian folk medicine and currently popular as it is said to protect against EMF.
Noble shungite is a form of amorphous carbon, which contains some (a tiny proportion) of natural fullerenes. It is also nearly 2 billion years old and almost certainly biological in origin. There are two types of shungite, noble shungite has concodial fracture and is shiny with a silvery lustre. The other variety is less ancient and does not show any evidence of fullerene bonding.