Lead isotope analysis is a technique for determining the source of ore in ancient smelting. Lead isotope composition is a signature of ore deposits and varies very little throughout the whole deposit. Also, lead isotope composition is unchanged in the smelting process.
The amount of each of the four stable isotopes of lead are used in the analysis. They are Pb, Pb, Pb and Pb. Ratios: Pb/Pb, Pb/Pb and Pb/Pb are measured by mass spectrometry. Apart from Pb, the lead isotopes are all products of the radioactive decay of uranium and thorium. When ore is deposited, uranium and thorium are separated from the ore. Thus, deposits formed in different geological periods will have different lead isotope signatures.
:::::::U →Pb
:::::::U →Pb
:::::::Th→Pb
For example, Hauptmann performed lead isotope analysis on slags from Faynan, Jordan. The resulting signature was the same as that from ores from the dolomite, limestone and shale deposits in the Wadi Khalid and Wadi Dana areas of Jordan.