New York Paper - Geology of the Exposed Treasure Lode, Mojave, California

The Exposed Treasure gold-mine has, for the past four years, been one of the largest producing mines of Southern California, its annual output havirig con~tituted I per cent. of the total gold and silver production of the entire State. At the present moment the property is idle, owing to the large quantity of water encountered on the lower levels, which will require the installation of a powerful pumping-plant before operations call be recommenced. Moreover, a prompt change in the character of the ore has occurred at water-level, which makes imperative an extensive campaign of development in the region of the un-oxidized ores before a plant adapted to their treatment call be definitely decided upon. The character of the changes encountered in these deeper ores makes the geology of this deposit a matter of importance, riot only for the immediate district, but for the desert region of Southern California in general, where many mines exist having in the oxidized belt conditions that, in many respects, resemble those in the Exposed Treasure mine. The deposit is situated in an apparently isolated butte about 2.5 miles south from the town of Mojave, on the Mojave desert. The butte, though apparently isolated, is in Fact geologicallg part of an extinct volcano, known as Soledad butte, which rises out of the plain 1.5 miles SW. of' the mine, to an altitude of 4,650 ft. above sea-level. Other buttes also rise from the desert plain toward the south and east, and again to the westward, all being closely related geologically to Soledad butte,—the whole constituting a single system as to origin and time. Since the end of the period of active volcanism in this region, there has been extensive denudation, the ancient plateau having been dissected during an epoch of apparently exces-