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Lead isotope analysis


Lead isotope analysis is a proven method for determining the origin of raw materials, especially in archaeometry.


The lead isotope ratios can be used in different materials (metal, glass, ceramics, pigments, etc.) on the one hand for classification and on the other hand for determining the origin of the raw materials. An example is the question of whether two objects are made of the same material or not. In the case of a group of objects it can be checked whether they consist of the same material or of different materials with possibly different origins. For the determination of the origin it is important to formulate a precise question, because a suspected link of origin between object and deposit can be answered unambiguously negative if there is no match. However, a positive assignment is not mandatory as long as all other possible areas of origin cannot be excluded. Therefore, a comparison with a database of deposits is necessary.

Ensuring the quality and reliability of our analyses is the constant focus of our laboratory. Therefore, we carry out control analyses on certified standard materials for each series of measurements. The most important reference material for this is SRM 981, a lead wire certified by the American Society for Testing and Materials in Washington DC and used internationally to check the accuracy of the analyses.


The isotope composition of all elements on earth is, in the first approximation, the same and unchangeable everywhere. For light elements, however, there are small changes due to the different behaviour of the isotopes, especially in diffusion-controlled processes such as evaporation and condensation. For heavy elements like lead, the relative mass differences are too small for such effects. There are exceptions, however, due to the radioactive decay of some isotopes. For archaeometallurgy, isotope analysis of lead has proved particularly useful for determining the origin of metals. The radioactive decay of uranium and thorium to lead is decisive for this. As a result, three of the four stable lead isotopes are constantly being formed anew. This lead mixes with the lead already present, so that the average isotopic composition of lead has changed significantly since the formation of the earth and continues to change continuously. During the formation of a lead deposit, the lead is separated from uranium and thorium by natural processes and there is practically no change in the isotope ratios of the lead. It now depends on the geological age and the composition of the parent rock of the ore formation which lead isotope ratios are fixed in this way. In any case, they are usually different in different deposits, which can be used for investigations of origin. Since the lead isotope ratios cannot be changed by chemical reactions, they can be found unchanged in the finished products produced from them, regardless of the complications that make it so difficult to assign metal objects to deposits due to their chemical composition, such as preparation, smelting, refining and, if necessary, corrosion. Therefore, the lead isotope ratios can be regarded as a kind of fingerprint of a deposit, which – unlike the chemical composition – is not changed on its way from the deposit to the finished product. The method also works for other metals and materials. However, the prerequisite is that the lead as a by-element together with the material in question comes from the same deposit.


The prerequisite for determining the origin is the assumption that the material originates from a single storage site. If there have been mixtures of materials from different storage sites, it is usually no longer possible to identify them. It should also be noted that in case of higher lead contents, the origin of the (added) lead and not of the base material is determined. The decision whether lead was added intentionally or not depends on the material and on the experience gained from many thousands of analyses of cultural-historical objects.

Sample properties

The sample size depends on the lead concentration. Approx. 100 ng lead are required for the measurement, so that, for example, 0.1 mg of a sample with 0.1% lead content is sufficient in principle. In practical operation, however, we usually use 10 mg or more. For materials with very low lead contents of 0.0001% (e.g. some minerals or solid copper) several 100 mg are necessary.