If the rocks don’t have a “skin”, or oxidation layer on the outside of them, you can get a good idea what the rocks will look like when polished by cleaning them thoroughly, and then wetting them down with water and looking at them in sunlight. Agate, japser, carnelian, petrified wood, petrified palmwood, and lots of other collectible stones can be found in different places in South Texas.
Is there a rock and gem club where you live? The best way to identify stones is often to show them to experienced rockhounds. If you don’t belong to a gem club, consider joining one. For usually less than $25 a year, you can meet new friends, go on field trips, and gain access to a clubhouse full of equipment and classes that teach you how to use it.
If you wish, you can take some photos of the rocks in good light when they’re wet, and send them to me at firstname.lastname@example.org. Perhaps I can help you identify them, or refer you to someone who can.