* ''Uranium prospecting''. Most of the “uranium” signal actually comes from the tenth decay process in the uranium series, the decay of bismuth-214. This is separated in time from the original uranium by half-lives in excess of 10<sup>9</sup> years, so the relatively soluble uranium may have moved away during the interim even though the log still records its presence. | * ''Uranium prospecting''. Most of the “uranium” signal actually comes from the tenth decay process in the uranium series, the decay of bismuth-214. This is separated in time from the original uranium by half-lives in excess of 10<sup>9</sup> years, so the relatively soluble uranium may have moved away during the interim even though the log still records its presence. |