I wonder how they got the ore out of the labyrinth of tunnels. No tracks, no ore cars, not enough room for animals. Just slaves skidding wicker baskets along? No steel for picks or shovels, either.
Even today, primitively operations will hand sort and high grade the ore and carry it out in wicker baskets on their backs. Silver ore is fairly soft so pounding stones of flint or quartzite would work well.