Wyoming bentonite has been mined for decades. Mining leases are not comparable to oil and gas leases principally because the risk of production is so dramatically different for the industries. I hold both types. Warning. One of the uses of bentonite is in the oil and gas drilling mud business so be careful that a bentonite lease doesn't compromise oil and gas leasing. Its tricky business.
Mining royalties can be extremely complex and often depend on what is removed rather than what is sold. Measurement and payment provisions are usually auditable in mining since the volumes effected over time represent big dollars for the land owner if handled properly. Mining in Wyoming is less regulated than oil and gas.
Gary L Hutchinson