As you move into a different chapter as from five to seven do you still need the granite mines and copper mines as mine are full up, and there does not seem to be any use for these resourses
The only use for copper and granite after you've left the Dwarves chapter is to build Dwarven roads, if you still want to do that. If you aren't able to collect the goods then that may mean that you have already deleted the portal, but not the mines which have goods ready. You won't be able to collect those goods now unless you rebuild the portal.