The mineral reserves are already public property as prescribed by the Chilean Constitution:
> The State has absolute, exclusive, inalienable and imprescriptible domain over all mines, including guano deposits, metalliferous sands, salt mines, coal and hydrocarbon deposits and the other fossil substances, with the exception of superficial clays, despite the ownership held by individuals or body corporates over the land in which the above should be contained. The superficial landed property shall be subject to the obligations and limitations prescribed for by law to facilitate exploration, exploitation and development of said mines.
What changes is that new mining concession will no longer be granted without accepting a majority stake from the state in exchange for the right to mine those deposits. The profit split might be different though, allowing firms to recover the capital.