The CO2 expenditure of the whole operation, including mining, milling, and transport, has been calculated to be about 4% of the amount of CO2 that is captured by the olivine. The financial cost of mining, milling, and transporting rock is about $7/ton.

We are not planning to do any new mining for the first allotments of olivine though, as there are literally "tons" of piles of olivine-rich rock sitting as "tailings" on the property of old mines.

This already excavated rock was mined in the pursuit of the mineral deposits below it and are considered "waste" by these mines. Kind of like buying a used car instead of having a new one created, that rock's CO2 is already accounted for. So, in this case, we do not have to mine it, only transport (ideally in an efficient manner like a train) and then mill it and spread it on the beach.