When was the chalcolithic period

In a strict sense this is not a true period at all. The word Chalcolithic is a term conveniently but loosely used to describe a culture which is still essentially Neolithic in character, but in which the metal copper is just beginning to be used, without, however, replacing stone as the principal material for implements. Chalcolithic cultures are thus transitional.

People in many areas of the world did not pass through this intermediate stage, but obtained their first knowledge of copper directly from other peoples who had already fully developed the art of copper metallurgy. The dates of Chalcolithic cultures differ everywhere, depending upon the time which it took for the knowledge of metal-working to spread. The earliest cultures in which copper has been found are in the Near East, and their estimated date is somewhere between 4000 and 3500 B.C. Copper did not appear in Europe much before 2000 B.C.