The Chalcolithic (Ancient Greek: χαλκός khalkos "copper" + Ancient Greek: λίθος lithos "stone") period or Copper Age, also known as the Eneolithic/Æneolithic (from Latin aeneus "of bronze"), 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 Ages. It appears that copper was not widely exploited at first and that efforts in alloying it with tin and other metals began quite soon, making distinguishing the distinct Chalcolithic cultures and later periods difficult. The boundary between the Copper and Bronze Ages is indistinct, since alloys sputtered in and out of use due to the erratic supply of tin.