One of the basic mineral resources of Texas is abundant deposits of lignite in Eocene rocks of the Gulf Coastal Plain. Currently, Texas lignites are utilized as sources of industrial fuel, activated carbon and, locally, drilling mud additives; research indicates significant future nonfuel uses of lignite and lignitic coals.

Studies of physiographic relations and of fossil molluscan faunas made in the Pecos River valley region (Val Verde County to the Texas�New Mexico border) reveal extensive, well-pedimented surfaces southwest of the river extending from the Davis Mountains to near the present channel.