This video is a good overview of the discovery and history of Uranium and how it is used to make an atomic bomb.  A couple of minutes into the video they clearly tell us that silver mining and uranium mining are correlated.  For over 400 years miners in the Czech Republic followed silver veins until the silver ran out and the veins were filled with a 'useless' black rock called Pechblende.  Pech means unlucky.

They had piles of this Pechblende laying around as it was of no value. Then in the early 1900's Uranium was discovered and it suddenly these piles were of immense value.  American scientists knew Germany had access to these piles of Uranium and they urged President Roosevelt to start an American project to investigate Uranium.  This was the beginning of the Manhattan project.

I believe transmutations are caused deep in the rock by some electric phenomena.  The heavier elements are created in-situ.  Silver is found in the central parts of the currents and Uranium is found out towards the ends.