The Chalcolithic or Copper Age is the transitional period between the Neolithic and the Bronze Age.[1]
It is taken to begin around the mid-5th millennium BC, and ends with the beginning of the Bronze Age proper, in the late 4th to 3rd millennium BC, depending on the region.
The development of states—large-scale, populous, politically centralized, and socially stratified polities/societies governed by powerful rulers—marks one of the major milestones in the evolution of human societies. Archaeologists often distinguish between primary (or pristine) states and secondary states. Primary states evolved independently through largely internal developmental processes rather than through the influence of any other pre-existing state.
^The New Oxford Dictionary of English (1998) ISBN0-19-861263-X, p. 301: "Chalcolithic /,kælkəl'lɪθɪk/ adjectiveArchaeology of, relating to, or denoting a period in the 4th and 3rd millennium BCE, chiefly in the Near East and SE Europe, during which some weapons and tools were made of copper. This period was still largely Neolithic in character. Also called Eneolithic... Also called Copper Age - Origin early 20th cent.: from Greek khalkos 'copper' + lithos 'stone' + -ic".