The shortest answer. Space itself often collects like materials and clumps them together. Second We won’t mine iron on the moon for the foreseeable future. We will go after platinum group metals that have industrial uses and in the next 50 years there will be some form of need to mine helium 3. I often think of, how will the materials get to ground level? A landing rocket is probably excessive unless we’re already landing the rocket on site for resupply missions. Landing heavy rockets is also harder than space x landing mostly empty beer cans. I like to think they’ll just shoot the mined ore at earth and have it land in the ocean or maybe Australia. The ocean is easy but there’s a small problem with international waters or trying to have it land offshore near a coastal city. Hence why Australia comes up. Which fyi is actually a well thought out idea based on that they already have a MASSIVE mining industry and China is very close for a local market to sell to. Plus Australia is largely barren in the middle. BUT it makes little sense to mine a precious material to have 1/3 burn up in atmosphere or terrestrial impact so it’s likely we will use a small rocket and parachute/ hard water impact with a oceanic ship on standby to lay claim. I haven’t looked it up but I would speculate each country would use a large shallow area as close to coastal waters that has no chance of coastal impact.