Abstract
The theoretical substantiation of the process of elimination of individual chemical elements from crystal lattices of metals in the process of the crystal-chemical transformations taking place during the long history of artifact existence was given. To confirm the theoretical conclusions, five ancient gold items from different historical periods (from the IV century B.C. to the XVIII century A.D.) with approximately the same contents of gold, silver, copper, and iron in the alloy body were studied. The conducted studies will promote more exact attribution of historical artifacts made of metals and revealing the signs of forgery or restoration.
 The chemical composition of items was determined immediately under patina and in the alloy body using a scanning electron microscope equipped with an energy dispersion spectrometer. The results have shown a much lower gold content inside the alloy than in the item surface. At the same time, the undamaged surface cleansed of mineral crusts contained significantly fewer impurities than the polished surface which did not have contact with the environment. Therefore, the study of the chemical composition of gold artifacts cannot be conducted solely based on surface studies.
 The studies have resulted in establishing a dependence of the concentration of the main component (gold) of the alloy in the artifact surface on the item age in thousands of years. Equations for predicting the age of the items that are chemically belonging to the described item group were also presented.
 Studies of peculiarities of crystal-chemical processes are very important in practice to prove the historical artifact authenticity, adjust artifact dating, identify signs of forgery or profound changes caused by restoration
Highlights
Experience in conducting analytical studies of the chemical composition of historical artifacts made of metals indicates the presence of traces of complex material transformations at the aggregate level and at the level of structure of individual crystals [1]
The results indicate the need for the studies with sets of items having approximately the same base chemical composition differing from each in their gold contents within 10 %
Chemical composition of gold artifacts was determined immediately under patina and in the alloy body using a scanning electron microscope equipped with an energy dispersion spectrometer
Summary
Experience in conducting analytical studies of the chemical composition of historical artifacts made of metals indicates the presence of traces of complex material transformations at the aggregate level and at the level of structure of individual crystals [1]. The traces of material transformations are well identified by means of electron microscopes and X-ray fluorescence analyzers They represent special recrystallization structures and are accompanied by precipitation of impurity elements, so-called patina, which form mineral crusts on the artifact surface. The processes of internal recrystallization of metals occur because of size changes in the ions that form the crystal lattice and in the impurity ions brought about by radioactive decay. ‒ establish probable dependence of gold concentration in the artifact surface on the item age on a condition that the initial concentration of gold was the same during the item manufacture
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