If you sell your mineral rights or oil & gas royalties, the IRS indicates that the sale can be treated one of two ways:
Your sell could be treated as the sale of business property which would be reportable as a section 1231 gain or loss reportable on form 4797.
Depending on how the property is held, the income or loss from the sale may be reportable as a capital gain or loss on Schedule D.
Make sure you discuss the sale with your attorney or CPA to ensure proper reporting on your tax return.