The region comprising the headwaters of the Owens River consists of uplifted granitic rocks of the Sierra Nevada Batholith to the west and extensive volcanic tablelands and terrane to the east. The volcanic features of the area are world-famous and include Devil's Postpile National Monument. The volcanic nature of the Mono Lake region is well-documented. Volcanic cones occur 5 miles southeast of Mammoth Lakes and 5 miles north of the lakes. Many local features and landmarks attest to the volcanic nature of the area south of Mono Lake including Pumice Valley, Crater Mountain, and Glass Mountain. Based on the great abundance of rhyolite and pyroclastic debris, most of the volcanism in this area was quite violent.
Volcanic activity has occurred in the area throughout most of its history. The Mono Lake region of eastern California is the center of an ancient and sporadically active source of volcanism extending from Silurian times virtually to the present! Metavolcanic rocks of early Paleozoic age (Silurian and Devonian), late Paleozoic age (Carboniferous and Permian), and early Mesozoic age (Triassic and Jurassic) can be found in the area. Indeed, most of the Ritter Range consists of Triassic and Jurassic metavolcanic rocks. Younger volcanics of Tertiary, Quaternary, and even recent age occur in the area, with Quaternary silicic rocks being the most common.
Virtually every account of the Lost Cement Mine places it at or near the headwaters of the Owens River. The ore is almost invariably described as a strange reddish cement filled with lumps of gold. This curious gold-bearing cement reminds one of the rusty red "calcrete" deposits of Western Australia. Some truly incredible gold nuggets have been recovered from these cemented, hematite-rich deposits. Could the Lost Cement ledge be a "calcrete-like" sedimentary deposit or is it indeed a strange and unique lode deposit? Prospectors may want to concentrate on the headwaters of the Owens River, especially up near the divide that