Uranium isotopes dating
In addition there is another stable isotope, lead 204, that is entirely primordial and does not form via radioactive decay at all.
Thus any of the radioactive isotopes and its lead daughter product can be used for dating, or a combination may be used.
So when a mineral grain forms (specifically, when it first cools below its trapping temperature), it effectively sets the uranium-lead "clock" to zero.
Lead atoms created by uranium decay are trapped in the crystal and build up in concentration with time.
The growth of U, can be used over a time range from a few hundred to half a million years.
Calcite precipitated from running or dripping water in springs and caves, as well as marls and soil-deposited calcretes may be spatio-temporally associated with archaeological materials; they can be dated by U measurements with a precision of ±5–10% of the age (by alpha counting) or ±1% (by mass spectrometry).
The 235U–207Pb cascade has a half-life of 704 million years and the 238U–206Pb cascade is considerably slower, with a half-life of 4.47 billion years.
If nothing disturbs the grain to release any of this radiogenic lead, dating it is straightforward in concept.