Decaying radioactive particles in solid rock cause sperical zones of damage to the surrounding crystal structure. A speck of radioactive Uranium-238 will leave a discoloration for each element it produces in it's decay chain to lead-206. Polonium isotopes decay very quickly (Half-life of 3 minutes). Rings created by polonium decay are often found embedded in crystals without the parent uranium halos. The polonium had to get into the rock before the rock becomes solid, but it cannot derive from uranium in the rock, or there would be a uranium halo. EITHER THE POLONIUM WAS CREATED PRIMORDIAL (NOT DERIVED FROM URANIUM) OR THERE HAVE BEEN RADICAL CHANGES IN DECAY RATES IN THE PAST.

< Kenny, 16