Answer: Copper
Notes: Copper was first used by humans as early as 9000 BCE. Ancient civilizations such as Mesopotamians and Egyptians used copper for tools, ornaments, and medical purposes. Copper is denoted by the symbol Cu and has an atomic number of 29. Evidence of copper usage has been found in archaeological sites dating back several millennia. Copper is a reddish-brown metal and an excellent conductor of electricity.
