Is it permissible for the state to lease out its land to a gold or oil exploration company, given that leasing is valid for usufructs and not for the corporeal objects themselves?

It is not permissible to lease land for the extraction of gold or oil from it, because leasing is valid for usufructs, not for specific tangible assets. Gold and oil are specific tangible assets that cannot be owned through a lease contract, and due to the significant uncertainty regarding the quantity that will be extracted from them. The legitimate method is for the state to hire these companies for a known wage or a known percentage for exploration, and whatever is extracted belongs to the state. There is another way to deal with exploration companies, which is to deal with a known share of what they will extract of gold and oil.