Gail, before the first decade of the 20th. Century mineral rights were conveyed with the sale of the surface.  If your predecessors owned land and sold it after 1900 there is the possibility that there was a reservation of mineral rights contained in the deed of sale.  Reservations became more common as years went by so the further into the 20th Century the greater  the chance of a mineral reservation.  Any ownership prior to 1900 is likely irrelevant.