Analyze the relationship between 'Pebble Mine' and 'copper' within the context of the input sentence.
Options: chief executive officer, product/material produced, legal form, position held

Before going to Kotzebue, Obama went to Dillingham, home to one of the world's largest sockeye salmon fisheries, where residents are fighting the Pebble Mine copper and gold project that has been proposed by Northern Dynasty Minerals Ltd .
product/material produced