The second highest spring temperatures in Humboldt County are reported from about 1.5 km north of Pinto Mountain. These springs, shown in Secs. 17, 19, T40N, R28E on the Pinto Mountain 7.5-minute Quadrangle map, are East and West Pinto Hot Springs, respectively. Location data given in older references are somewhat confused, owing to the irregular nature of the land grid in this area. Reported temperatures for the springs, which are about 1.5 km apart, are 93-94°C. The water analyses are also quite similar, indicating a close hydrologic connection. The springs are in a small outcrop area of quartz monzonite (Willden, 1964, plate 1) in some low hills of mafic Tertiary volcanic rocks along the west margin of the Black Rock Desert. The estimated thermal reservoir temperatures using the conductive silica geothermometer are 162-165°C (Mariner and others, 1974), although later estimates using the Na-K-Ca geothermometer indicated reservoir temperatures of 173-176ºC (Mariner and others, 1983, p. 105; White and Heropolous, 1983, p. 50). Travertine and siliceous sinter are interlayered in the spring deposits at the springs (Hose and Taylor, 1974), and the presence of cinnabar is reported (George Berry, in unpubl. report to Sun Oil Co., 1963). Batzle and others (1976) reported on telluric profiles at Pinto Hot Springs.