From Academic Kids
The Chalcolithic (Greek khalkos + lithos 'copper stone') period, also known as the Eneolithic or Copper Age period, is a phase in the development of human culture in which the use of early metal tools appeared alongside the use of stone tools.
The period is a transitional one outside of the traditional three-age system, and occurs between the neolithic and bronze age. It appears that copper was not widely exploited at first and that efforts in alloying it with tin began quite soon, making distinguishing distinct Chalcolithic cultures and periods difficult.
Because of this it is only applied by archaeologists in some parts of the world, mainly south-east Europe and Western and Central Asia where it appears around the first half of the third millennium BC.
The European Beaker people are often considered Chalcolithic as were the cultures which first adopted urbanisation in south west Asia. Many megaliths in Europe were erected during this period and it has been suggested that the Proto-Indo-European language group dates to around the same time.
ִzi the Iceman, found in the ִztaler Alps and whose remains have been dated to about 3300 BC, carried a copper axe and flint knife. He appears to have been in a region of Europe which was transitioning through this period at that time.