Not the person you responded to but my 2cents. You expect to find the vast vast majority of materials for this self replicating mining equipment as well on the

Not the person you responded to but my 2cents. You expect to find the vast vast majority of materials for this self replicating mining equipment as well on the same asteroid? For them to put up the huge amounts of energy generation, materials refining and self fabrication for them to do a large amount of tasks and build reentry packages without us sending a lot of stuff into space lest we very easily surpass the impact of mining on earth. We'll have to get very very creative with nickle-iron and silicates to build a small automata civilization on big flyby rocks.