Mont. Code § 70-19-202
If a person assumes and exercises exclusive ownership over or takes away, destroys, lessens in value, or otherwise injures or abuses any property held in joint tenancy or tenancy in common, the party aggrieved has action for the injury in the same manner as the aggrieved party would have if the joint tenancy or tenancy in common did not exist. However, this section does not prevent one cotenant or joint tenant or any number of cotenants or joint tenants acting together from entering on the common property at any point or points not then in the actual occupancy of the nonjoining cotenants or joint tenants and enjoying all rights of occupancy of the property, without waste and, in the case of mining property, from mining the property in a minerlike manner and extracting, milling, and disposing of the ore from the common property, paying its or their own expenses and subject to accounting to the nonjoining cotenant or joint tenant for the net profits of the mining operations. All liens for labor and materials incurred in the mining attach only to the undivided interest or interests of the working cotenants or joint tenants, but nothing in this section prevents or precludes the cotenant or joint tenant, not joining in the operation of the mining property, from receiving the cotenant's or joint tenant's proportionate share of all ore or ores on the dump upon payment or tendering payment of the actual cost of mining the property.
§ 70-19-202, MCA