10 Unsolved Mysteries of the World, No-10

Throughout the most recent couple of decades, mineworkers in South Africa have been uncovering baffling metal circles. Starting point obscure, these circles measure roughly an inch or so in distance across, and some are carved with three parallel sections circling the equator. Two kinds of circles have been discovered: one is made out of a strong somewhat blue metal with bits of white; the other is burrowed out and loaded with a supple white substance. The kicker is that the stone in which they where found is Precambrian – and dated to 2.8 billion years of age! Who made them and for what object is obscure.