That is essentially what I did last night and it does sort of work on a small scale. I nibbled rocks until one produced a fragment with Samarium in it. Then launched a prospect at it, released a collector, put all my power to weapons and mined like a demon possessed.... albeit slowly

In not too much time I had the 2 units I needed for the mission and more.... and just as I was about to leave, it was stolen

. So, armed with the knowledge that this worked, I decided to try a different belt. Unfortunately, I chose one in the wrong direction and ended up leaving the new player area, so after all that time, effort and hours of frustration.... the mission was rescinded because I can't get back there to hand it in, even if I did go and mine it again. So I refit for courier/data missions.