Vermiculite deposits in the Central Mineral region of Texas, chiefly in Precambrian metamorphic rocks, are situated in Llano County and adjacent parts of Mason, Gillespie, and Burnet counties with minor occurrences in Blanco and San Saba counties.
About 10 miles south of Van Horn, Texas, the Van Horn Mountains rise abruptly above an intermontane plain and extend southward to the Sierra Vieja. The area lies primarily in the southwestern part of Culberson County but extends into Hudspeth and Jeff Davis counties.
The first entry in the Guidebook Series details a field excursion to the Eastern Llano Region of Central Texas in 1958. Retrace the footsteps of Virgil Barnes and the other state geologists in attendance:
Stop 1. Honeycut Bend
Stop 2. High-calcium reef, Marble Falls area, Burnet County
At the northern end of the Coahuila platform, the thinned Comanchean sequence consists of the newly named Sixshooter group of carbonate formations underlain by the newly named Yearwood formation.