Dating can be done by radiocarbon dating or other techniques which look at the amounts of elements like iron or potassium. It is the assumed that the tool is approximately as old as the rock which surrounds it.
How are artifacts dated?
Very few artifacts recovered from an archeological site can be absolutely dated. Archeologists use several methods to establish absolute chronology including radiocarbon dating, obsidian hydration, thermoluminescence, dendrochronology, historical records, mean ceramic dating, and pipe stem dating.
Do archaeologists get to keep what they find?
Professional archaeologists do not keep, buy, sell, or trade any artifacts. Quite simply, they dont get to keep what they find because it doesnt belong to them. If archaeologists kept what they found, they would be the only ones to know the story behind the object. Archaeologists want to share their discoveries.