By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Until the discoveries at Goldfield in 1902, the gold deposits of Esmeralda County were in themselves relatively insignificant; most of the gold had been produced as a byproduct of rich silver ores. Yet, gold was the metal sought in the early days, and in at least one instance, at Gold Mountain in the Divide district, the search for gold led to the discovery of rich silver deposits.
The silver-gold deposits of the county are of two general types: veins associated with granitic bodies of Late Jurassic or Early Cretaceous age, and fissure filling in Tertiary volcanics. The deposits at Silver Peak, Windypah, Hornsilver, Lida, Montezuma, and Klondike belong to the first type; those at Divide and Goldfield to the second. Production in the county from 1903 through 1959 was 4,912,112 ounces of lode gold, mostly from Goldfield, and 2,071 ounces of placer gold.
The Divide (Gold Mountain) district, 5 miles south of Tonopah, has been primarily a silver camp; it was founded in 1901. Between 1901 and 1917 there was only sporadic exploitation of the gold-bearing veins on Gold Mountain and the silver lodes in the Crown Divide property. Then, in 1917, a rich silver lode was discovered on Gold Mountain which immediately created a boom that lasted until 1919. The principal mines in the district are the Tonopah Divide, the Divide Extension, and the Tonopah Hasbrouck (Knopf, 1921b, p. 148-170).
Gold production from 1910 through 1959 was 26,483 ounces, mostly as a byproduct of ores mined for silver.
The predominant rock in the district is the Fraction Rhyolite Breccia (of the Siebert Formation) of probable late Miocene age. Several stocks of Oddie Rhyolite and Divide Andesite (of late Miocene age) intrude the rhyolite breccia. Latite flows of Pliocene age cap the higher peaks. The ore bodies are mineralized fracture zones in the Fraction Rhyolite Breccia. Cerargyrite is the main silver-bearing mineral; some sooty argentite is present, and molybdite and powellite are abundant locally. A few narrow gold-quartz veins have been found in the Oddie Rhyolite. Veinfilling in these consists of rhyolite fragments, quartz, and pyrite.
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