Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable.

Unlike any other method, uranium-lead has a natural cross-check built into it that shows when nature has tampered with the evidence.

There is also primordial Pb that the earth acquired when it formed, its isotopic composition determined as that of troilite in the Canyon Diablo iron meteorite.

Subsequently new crustal rocks formed via partial melts from the mantle.

However, each of them also occurs, to some extent, as primordial isotopes that were made in supernovae, rather than radiogenically as daughter products.

U-Pb radioisotope dating is now the absolute dating method of first choice among geochronologists, especially using the mineral zircon.

A variety of analytical instruments have also now been developed using different micro-sampling techniques coupled with mass spectrometers, thus enabling wide usage of U-Pb radioisotope dating.

Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide.

The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively.