Proper age gap for dating
His view was based on what may be the first in-depth lithic analysis of the objects in his collection, which led him to believe that they are artifacts and to suggest that the historical evolution of these artifacts followed a scheme.
Mercati examining the surfaces of the ceraunia noted that the stones were of flint and that they had been chipped all over by another stone to achieve by percussion their current forms.
The name ceraunia, "thunderstones," had been assigned.
Ceraunia were collected by many persons over the centuries including Michele Mercati, Superintendent of the Vatican Botanical Garden in the late 16th century.
It is, however of little or no use for the establishment of chronological frameworks in sub-Saharan Africa, much of Asia, the Americas and some other areas and has little importance in contemporary archaeological or anthropological discussion for these regions.
The concept of dividing pre-historical ages into systems based on metals extends far back in European history, probably originated by Lucretius in the first century BC, but the present archaeological system of the three main ages—stone, bronze and iron—originates with the Danish archaeologist Christian Jürgensen Thomsen (1788–1865), who placed the system on a more scientific basis by typological and chronological studies, at first, of tools and other artifacts present in the Museum of Northern Antiquities in Copenhagen (later the National Museum of Denmark).
He later used artifacts and the excavation reports published or sent to him by Danish archaeologists who were doing controlled excavations.
The three-age system is the categorization of history into time periods divisible by three; for example, the Stone Age, Bronze Age, and Iron Age, although it also refers to other tripartite divisions of historic time periods. Thomsen, director of the Royal Museum of Nordic Antiquities, Copenhagen, as a means to classify the museum’s collections according to whether the artifacts were made of stone, bronze, or iron.
In history, archaeology and physical anthropology, the three-age system is a methodological concept adopted during the 19th century by which artifacts and events of late prehistory and early history could be ordered into a recognizable chronology. The system first appealed to British researchers working in the science of ethnology who adopted it to establish race sequences for Britain's past based on cranial types.