The Union district, in northwestern Nye County in the Shoshone Range (lat 38"55' N., long 117"35' E.), was organized in 1863, and the town of lone was soon built. After a few brief flurries of activity which yielded about $1 million in gold and silver by 1880 (Lincoln, 1923, p. 196), the district became almost dormant. The discovery of cinnabar in 1907 revived activity somewhat, and since then production of mercury has been fairly consistent; however, gold production from 1903 through 1959 was only 748 ounces. Total gold production cannot be ascertained, but it is assumed that at least 10,000 ounces was produced before 1903.
The oldest rocks in the district are meta-andesites of Carboniferous age (Krai, 1951, p. 196). These are overlain by Triassic slates, limestones, and conglomerates. A small granodiorite stock cuts the sedimentary rocks. The youngest rocks in the area are Tertiary rhyolite and andesite. The mercury and gold deposits are associated with the Tertiary rocks; however, the ore at the Berlin mine, the largest mine in the district, consists of lead-copper-zinc-antimony sulfides in quartz veins in the Carboniferous meta-andesites (Krai, 1951, p. 199-200).
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