By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Piute County, one of Utah's smaller counties, is in the south-central part of the State and is immediately east of Beaver County. Gold lodes in the Tushar Range in the western part yielded most of its mineral wealth; through 1959 about 240,000 ounces was produced, mainly from the Gold Mountain and Mount Baldy districts. Silver, lead, and copper were also mined on a smaller scale.
Gold-bearing sand was discovered in about 1868 in Pine Gulch Creek in the Ohio district about 6 miles southwest of Marysvale. Later in the same year gold lodes were found (Butler and others, 1920, p. 541). Discoveries of lodes immediately north of the Ohio district led to the organization of the Mount Baldy district in 1878. Data from these two districts are combined in this report.
After the successful introduction of the cyanide process, interest was concentrated on an area north of the Mount Baldy district that contained gold deposits which previously had resisted the amalgamation treatment. These deposits were developed, and by 1889 the Gold Mountain district was organized (Butler and others, 1920, p. 540). Mining flourished in the county until 1941, after which activity decreased; production remained small through 1959.
GOLD MOUNTAIN DISTRICT
The Gold Mountain (Kimberly) district in the northwest part of Piute County is just south of the Sevier County line and about 10 miles west-northwest of Marysvale. Some deposits are in the adjacent part of Sevier County.
After the perfection of the cyanide process for treating complex ores, previously known gold-silver lodes were developed. The Gold Mountain district was organized in 1889, and a mill was built at the Annie Laurie mine which was to become the most productive mine of the area. During the most prosperous period, from 1901 through 1913, a total of 134,744 ounces of gold was mined, chiefly from the Annie Laurie and Sevier mines (Butler and others, 1920, p. 540-541).
Activity declined after 1914, and the district was virtually idle from 1918 to 1934. A brief resurgence occurred from 1934 through 1940 which was followed by intermittent small-scale activity through 1959. Total gold production through 1959 was about 159,000 ounces.
Bedrock in the Gold Mountain district consists of a basement of sedimentary rocks of pre-Tertiary age overlain by two groups of volcanic rocks - an earlier Tertiary (?) sequence of andesite, dacite, and quartz latite breccias and tuffs with a few intercalated flows predominantly of quartz latite and a later Tertiary (?) sequence of white rhyolite tuff with a few local interbedded quartz latite flows. The older sequence of volcanic rocks is intruded by masses of quartz monzonite (Callaghan, 1938, p. 98-100).
The ore deposits are silver and gold-bearing quartz veins 3 to 30 feet thick in the earlier Tertiary (?) volcanic rocks. The ore minerals are gold, finely divided argentite, and pyrite in a gangue of quartz, carbonates, adularia, and barite (Lindgren, 1906a). Locally the veins contain copper stains and quicksilver (Butler and others, 1920, p. 544).
MOUNT BALDY DISTRICT
The Mount Baldy (Ohio) district is on the east side of the Tushar Range about 6 miles southwest of Marysvale. The early records of the district are fragmentary, but the first mineral discoveries in the Ohio camp were made about 1868 and in the Mount Baldy camp about 1878. Though many claims were located in both camps, early production apparently was small; records show an output of 8,000 to 10,000 tons of ore from 1868 to 1903 (Butler and others, 1920, p. 542).
Mining was intensified from 1910 through 1940 but was sporadic thereafter. No activity was reported in 1959. Production before 1904 cannot be determined (Butler and others, 1920, p. 542), but from 1904 through 1959 it was 77,500 ounces of gold, most of which came from lead-silver-gold replacement deposits in the Deertrail mine.
The geology is similar to that of the Gold Mountain district. Sedimentary rocks of Carboniferous, Triassic, and Jurassic ages are overlain by volcanic rocks of Tertiary age. The lowermost unit is a bed of quartzite more than 200 feet thick. It is overlain by interbedded dolomite and quartzite about 650 feet thick which contain Permian fossils near the top. A 500-foot-thick interval of Triassic limestone overlies the Permian rocks, and 2,100 feet of non-marine shales, sandstones, and quartzite overlies the Triassic rocks. Lying upon these nonmarine beds are limestones, shales, and sandstones of Jurassic age (Callaghan, 1938, p. 98-99).
The sedimentary rocks are overlain by Tertiary volcanic rocks, which are separated into two units. The lowermost unit, of earlier Tertiary (?) age, consists of volcanic breccia and tuff and a few interbedded flows predominantly of quartz latite. The upper unit, of later Tertiary (?) age, is mainly rhyolite tuff containing a few local flows of porphyritic quartz latite (Callaghan, 1938, p. 99-100).
All the rocks are cut by faults. The steep eastern and western flanks of the Tushar Range are bounded by fault systems, and within the range there are many faults parallel to the ones that bound it (Butler and others, 1920, p. 539-540). Throughout most of the area, the strata, though locally warped, dip toward the west and southwest (Callaghan, 1938, p. 102).
The ore deposits are in replacement bodies and veins. The Deertrail mine, which is the largest producer, is in a limestone replacement body, the only important deposit of this type in the district. Ore consists of oxidized products of galena and pyrite having a high gold and silver content. The gangue is sericite, quartz, and iron oxide. The ore body is a blanket deposit that replaced the upper part of a Jurassic limestone bed and possibly part of the overlying quartzite. At several places the ore is in two zones separated by 20 to 25 feet of unaltered rock (Butler and others, 1920, p. 550).
The vein deposits (Butler and others, 1920, p. 543-545, 555-557) occurred chiefly in the Ohio camp but their yield of gold and silver was small, and the yield of lead, copper, and zinc was smaller. However, some veins contain alunite and were of interest as a source of potash and alumina. The gold-silver veins occur almost exclusively in the volcanic rocks, where they occupy faults and fissures.
The typical gangue minerals are quartz, carbonate, and local barite, adularia, and fluorite. The ore minerals are galena, chalcopyrite, tetrahedrite, pyrite, and sphalerite. In the rich oxidized gold ore, the gold is in part free and may be combined with silver as a telluride. Most of the mined ore was oxidized.
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