The Squaw Creek quadrangle is partly within the Llano region and partly within the Edwards Plateau province. The Edwards Plateau is continuous along the southern border of the quadrangle, but erosion has dissected it until long fingers extend northward, the most important being between Mormon and Squaw Creeks and east of Squaw Creek. The geology of the Squaw Creek quadrangle is shown on a planimetric map, and the only topographic map available is the reconnaissance 30-minute Kerrville quadrangle.

Stonewall quadrangle is south of the Llano region and is in the marginal portion of the Edwards Plateau where much of the plateau surface has been destroyed by erosion. Along the southern edge, lobes of the Edwards Plateau are present, which coalesce southward to form a continuous narrow east-west plateau belt � part of which is just south of the Stonewall quadrangle. Most of the quadrangle is within the gently undulating, broad Pedernales River basin.

The Hazel mine is one of the oldest mines in Texas and has been the largest copper-producing property in the State. The mine has a recorded production of over 1 million pounds of copper and over � million ounces of silver, and there are a number of years in which the mine was active but for which no figures are available. True production is in the neighborhood of 4 to 5 million ounces of silver and 1� million pounds of copper. The Hazel mine is the most important of a group of mines and prospects known as the Allamoore�Van Horn copper district.

The Ellenburger of Texas was first defined as a marine limestone formation of Cambrian and Ordovician age (Paige, 1912), but recently it has been subdivided into several formations and the term Ellenburger given group status (Cloud and Barnes, 1948). The group forms an important unit in the geology of Texas, its known extent in both surface and subsurface covering approximately one-half of the State (fig. 1). Consequently the Ellenburger has received the attention of many geologists over a period of more than forty years.