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. All of the known deposits contain a lesser percentage of vermiculite than the deposits now being exploited in South Carolina and Montana; however, the deposits are substantial in size and will probably be mined when the richer domestic and foreign sources are exhausted.

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 mountains owe their present topographic form to late Tertiary block-faulting. Structurally, they are a northward-trending horst which is flanked on the east and west by intermontane basins.

Since 1947, the Morton Salt Company's Kleer mine in the Grand Saline salt dome has more than doubled in size. Balk's mapping of the salt structures in the pre-1947 workings showed that (1) the layers of salt near the southeastern border of the dome dip steeply southeast and south, presumably parallel with the dome border. Elsewhere the layers form intricate systems of folds. (2) The axes of all folds plunge nearly vertically. (3) Anhydrite and halite are elongated parallel to the nearest fold axis.