The High Rock country of northwestern Nevada forms the boundary between Washoe County and Humboldt County to the east. The area is remote, extremely rugged, and dominated by volcanic processes. Virtually the entire area encompassing the High Rock country is overlain by middle to upper Tertiary volcanic rocks consisting of basalt and andesite flows, rhyolitic lava flows and related shallow intrusives, and various silicic ash-flow tuffs and tuffaceous sedimentary rocks. The High Rock volcanics are part of a large caldera-derived complex made up of rhyolitic lava flows, ash flows, and dome structures overlain by younger andesite and dacite flows.
The geology at High Rock Lake is representative of the area as a whole. Rhyolitic lava flows occur just west of the lake while slightly less felsic welded tuffs comprise most of the slopes to the east. To the northwest, younger flows of andesite and dacite dominate the landscape.
The High Rock country is cut by three sets of normal faults, the most prominent of which trends roughly north-south. Basin and Range faulting has also produced two sets of faults, one trending northwest-southeast, the other northeast-southwest.
The High Rock region is bereft of any major mineral deposits. The rock types that comprise the rugged mountains near High Rock Lake are notorious for their lack of associated mineral deposits. Basalts, mafic andesites, ash-flow tuffs, and tuffaceous sedimentary rocks almost invariably lack any type of mineralization. The nearest zone of mineralization lies 15 miles south of High Rock Canyon, near the site of Leadville. Here, the ore bodies consist of small silver, lead, and zinc veins hosted in older Oligocene-age andesites and dacite porphyries.
The High Rock country presents a number of interesting problems to the enterprising prospector. The area is extremely rugged and remote and the volcanic rocks that overlie the majority of the region are not known for harboring significant mineral deposits. Nevertheless, the High Rock region may still be promising ground for the prospector. The area has not been heavily prospected and it is quite conceivable that a small but rich placer deposit of gold has been overlooked. And of course, as every prospector knows, gold is where you find it.