The test is used mainly in association with the fluorine test and radiometric assay, as in the cases of Piltdown and Swanscombe Man. The basis of cross-dating is the occurrence of finds in association.
So in the absence of geochronology, two cultural groups can only be proved contemporary by the discovery of links between them.
The radioactivity of an artifact's content determines how long ago the specimen was separated from equilibrium with the atmosphere-plant-animal cycle.
The method is based on the principle that all plants and animals, while they are alive, take in small amounts of rock carvings and engravings, potentially applicable to Paleolithic artifacts with a strong patina caused by exposure to desert dust.
Therefore, pottery which is baked in effect fossilizes" the Earth's magnetic field as it was the moment of their last cooling (their archaeomagnetism or remanent magnetism).
In areas where variations in the Earth's magnetic field are known it is possible to date a pottery sample on a curve.