RILEY MOUNTAINS. The Riley Mountains, the site of the Los Almagres Mine, are in south central Llano County between State Highway 16 and U.S. Highway 71 southeast of Llano. Elevations range from about 1,500 feet to 1,800 feet. The local terrain is generally rolling, with dense and deep dissection, covered with shallow and stony soils. Vegetation consists primarily of open stands of live oak, juniper, and mesquite.