One of the two largest prehistoric mines in the Balkans "Ai-Bunar" (Bear Well) was located near Stara Zagora. It is estimated that the annual number of people employed in the field of metallurgy and ore mining in it amounted to 3,000 people.

This large number of workers necessitated the introduction of a strictly organised hierarchical social structure. Order in the community was determined by the high priest-leader of the tribe. He performed two functions - administrative and spiritual, as he made contact with the gods, which strengthened his power and helped him govern his subordinates.

The most skilled workers in the mining industry were those who placed the wooden supporting structures in the mine, as the survival of the rest of the workforce depended on them.

Many of the participants in the metallurgical activity were carpenters and loggers. They provided the necessary wood and charcoal for heating the copper melting furnaces.

In the construction of metallurgical furnaces for melting copper, highly-precise skills were required, which led to a form of specialisation of employees in this branch of work.

The kilns were made of stone and plastered with incombustible ore. In addition to native copper, many ores with copper impurities were melted in them. Before being placed in the kiln, the large pieces were broken with stone hammers, then with the help of hand-operated stone mills, were crushed into small pieces and placed in the kiln. Since the metallurgical processing of copper was only possible past its melting point of 1084 Celsius degrees, a layer of ore was alternated with a layer of charcoal in order to reach a higher temperature. After melting, the ore was collected at the bottom and the slag was discharged through a hole.

The first labour tools produced during the Enolith completely imitated their stone prototypes from the late Neolithic. Later, the production and manufacture of more sophisticated and different products began. The products were first forged and later cast in earthen molds.

An extreme level of precision was required in the casting process to eliminate the side effects obtained from the mold. The molds were open and closed. Closed molds usually consisted of two parts, and were made of clay. The shape of one side of the object was carved in each half of the mold.

The tools produced from copper during the late Eneolithic were not intended for mass use in daily activities. They were a symbol of prestige and high social status. It is confirmed with the graves from the late Neolithic necropolises: Varna, Durankulak, Devnya or others, which were rich in metal artefacts. In addition to copper, people began to process gold. A typical example of this phenomenon is seen with the finds from the Varna Chalcolithic necropolis. Gold has usually been associated with gods and belief in the sun god. That is why the gold items were mostly ritual in nature.

The products and tools obtained from the processing of copper ore were under the control of a centralised power, which controlled the trade and use of copper and gold products. The development of metallurgy during the Eneolithic led to the formation and establishment not only of the first large production centers, but also the first large settlements. The first large tribal associations were created and they imposed their power over large territories and thus became the bearers of a form of statehood and the formation of social strata.