I don't know if this impacts Nautilus much but there was an article today at The Guardian about sand mining. I think the Nautilus plan is to land boatloads of aggregate in a major Chinese port. If I read it right the PEA did not explicitly evaluate what the aggregate, after ore is removed, might sell for.
Riddle of the sands: the truth behind stolen beaches and dredged islands
The insatiable demand of the global building boom has unleashed an illegal market in sand. Gangs are now stealing pristine beaches to order and paradise islands are being dredged and sold to the construction industry
https://www.theguardian.com/global/2018/...ed-islands
Sand Wars – China and developing countries need tens of billions tons of sand for urbanization and economic growth