FOSSIL KNOBS. The Fossil Knobs are two miles northwest of Terlingua in southwestern Brewster County (centered at 29°20' N, 103°38' W). They rise 3,234 feet above sea level and 430 feet above Farm Road 170, a mile south. The shallow, stony soils on the Fossil Knobs support oak, juniper, and some mesquite. The Fossil Knobs, like many other peaks in the area, are dotted with mines dating from the glory days of the Terlingua Mining District in the early 1900s.