The Stone-Copper Age covers approximately the period between 4000 and 3000 BC, with extensions in some parts of the world until later, and none in others. Most often, the Chalcolithic is considered an early stage of the Bronze Age, but some scholars consider it a separate period. During this era, copper tools of and labour instruments were used, which, while soft and fragile, were more precise and of higher quality than stone.
However, stone remains more common throughout the period because of the still primitive method of metal extraction and processing. During this period, people first discovered other metals such as gold and tin.
During the Copper Age, a hierarchical social system began to emerge and there was a greater division of labour than in previous eras. The most important find related to the Chalcolithic in Bulgaria is the Varna Chalcolithic Necropolis, which has unearthed the oldest processed gold in the world.