Most people when looking for land assume that the mineral rights come with the property. The truth is: they do not automatically convey! The further truth: the current seller probably doesn't own the mineral rights to even be able to convey them to you!
Finding land with the mineral rights is pretty rare around East Texas, although it does happen occasionally. In 8 years, I've seen one property have the minerals, and they reserved those minerals when they sold. With most properties, the mineral rights have been reserved from the very beginning, and passed to heirs of the original owner over the years. Real estate agents, nor the title company, research mineral rights.
To find out if a property has mineral rights to convey, the buyer will need to hire a Landman to research that out. They will research titles and abstracts for many years back to determine who actually owns the mineral rights.