Good advice so far. If you have the time and ability, you'll net a much better return if you sell these items yourself.
Something else to consider is your market. Since you're selling silver ore and gold nuggets, you might get a better return if you sell these items as mineral specimens. PM dealers will likely expect a discount on your unrefined ore while a rock/mineral collector might happily take your specimens as is. I'm not involved in the mineral collector market myself but it might be something worth investigating. Good luck!