What is the value of zakat on rikāz, and is finding a precious metal in the wilderness permissible?

If what you found is a lost item (Luqata), you must publicize it for a year, then you may own it. If it is a buried treasure (Rikaz), you must give out one-fifth of it. If it is a mineral, then Zakat is due on it if it is gold or silver, or if it has value and reaches the Nisab according to some scholars. It should be handed over to the state if the ruler prohibits the ownership of minerals.