Explanation:

gold, silver, copper, bronze but not iron

The Harappans did not know the use of Iron. Iron was not discovered by the Harappan people. Since it was a bronze age civilization, it had made many metallurgical advances in copper and bronze but not in Iron. Harappans procured raw material from other neighboring countries like Silver from Afghanistan, Iran, and Iraq, Lead from Kashmir, Rajasthan, Gold was obtained from Karnataka and Copper from Rajasthan. Iron was actually not known to Indus Valley Civilization people or Harappan people.