|Name||Mundy Breccia and Castner Limestone, undivided|
|Primary rock type||limestone|
|Secondary rock type||basalt|
|Other rock types||hornfels; conglomerate; dolostone (dolomite); diabase|
Sedimentary > Carbonate (Bed)Castner Limestone includes hornfels, conglomerate, dolomite, and diabase and is mostly light gray, green, and blue limestone, fine to coarse grained, lt. gray chert lenses, thin bedded, irreg. bedded in upper one-third; metamorphic minerals such as serpe
Metamorphic > Granoblastic > Hornfels (Hornfels)hornfels present in the upper third of the Castner Limestone, thus is ranked a minor part of the whole map unit (Mundy Breccia and Castner Limestone, undivided). Hornfels very fine grained, dark gray, in many thin beds, laminated and contains a few beds
Tectonite > CataclastiteThe Mundy Breccia randomly oriented, black basalt boulders, angular to slightly rounded, in matrix of dark gray mudstone. thickness about 90 ft, as much as 250 ft maximum.
Sedimentary > Carbonate (Bed)Dolomite in the basal exposed beds of the Castner Limestone in the Franklin Mtns. The dolomite is white to light gray, one bed contains algal structures
Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000
Bureau of Economic Geology, 1968, Van Horn-El Paso Sheet, Geologic Atlas of Texas: Bureau of Economic Geology, The University of Texas at Austin, scale 1:250,000.