By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Powell County is in west-central Montana, west of the Continental Divide and west of Lewis and Clark County. Most of the gold production has come from placer deposits in the southern part of the county. Gold-bearing gravels discovered along Gold Creek in 1852 were probably the first gold discoveries in Montana (Lyden, 1948, p. 118-120), although they were not mined until 1862.
The important placers of Powell County are in the Pioneer district, which includes the Gold Creek placers, and the Ophir and Finn districts. Gold lodes were worked in the Ophir and Zosell districts. Powell County through 1959 produced about 517,000 ounces of placer gold and about 50,000 ounces of lode gold.
The Finn district includes Washington, Jefferson, and Buffalo Gulches. Streams in the district along the western slope of the Continental Divide, about 15 miles north of Avon, have yielded moderate amounts of placer gold, mostly before 1890 (Pardee and Schrader, 1933, p. 114). The deposits were discovered in the early or middle 1860's and according to Raymond, as quoted by Lyden (1948, p. 128), they yielded gold worth about $1.5 million by 1869. The most productive placers in the district have been those along Washington Creek. After 1890 the placers in the district were worked intermittently; the two most prominent periods were 1908-16 and 1931-42. No activity was reported from 1951 through 1959.
The recorded production from 1908 through 1932 was about 1,480 ounces, and from 1933 through 1942, about 6,472 ounces. Less than 100 ounces were produced from 1942 through 1959. The total placer production of the district through 1959 was about 81,000 ounces.
From 1933 through 1959 the district also produced a little over 600 ounces of lode gold, probably from quartz lodes (Lyden, 1948, p. 128). No description of the geology of the area has been found.
The Ophir (Avon) district, which includes Nigger Hill, is on the west side of the Continental Divide and comprises several formerly productive placer deposits and lodes valuable for gold, silver, and copper.
The placer deposits were found in 1865, and the town of Blackfoot City, now called Ophir, was founded (Knopf, 1913, p. 15). The placer deposits along Carpenter Creek, locally called Ophir Creek, and its tributaries were the richest and most productive (Lyden, 1948, p. 126-128), but after 1875 they were largely exhausted and were worked in subsequent years by the Chinese. In 1934 a Yuba connected-bucket dredge was operated on Carpenter Creek, but in July 1935 it was dismantled (Lyden, 1948, p. 127). Only minor activity was reported from 1938 through 1954 and none from 1955 through 1959.
Pardee and Schrader (1933, p. 30) concluded that the value of the early placer production was at least $3.5 million (169,325 ounces) and Lyden (1948, p. 127) credited the district with a production of about $5 million (about 242,000 ounces). From 1908 through 1954 a minimum production of about 9,150 ounces was recorded, of which 8,460 ounces represents the output of the dredging operations in 1934-35. The total minimum placer output through 1959 was about 180,000 ounces.
Mining of lode deposits in the Ophir district began as early as 1888 (Pardee and Schrader, 1933, p. 32-35) and continued on a small scale and intermittently until 1954, the greatest activity being in 1909-18 and 1936-41. Lode gold output through 1959 was about 8,250 ounces; total lode and placer production was about 188,250 ounces.
The country rock in the Ophir district is limestone, shale, and quartzite of early Paleozoic age, intruded by small stocks of quartz monzonite of Cretaceous or Tertiary age (Pardee and Schrader, 1933, p. 30-35). The lodes are irregularly shaped pipelike replacement bodies in limestone and are genetically related to the quartz monzonite. Pyrite and chalcopyrite are the principal sulfide minerals in a gangue of quartz, and garnet, diopside, magnetite, and hematite occur locally. Tetrahedrite was found in some lodes, and gold tellurides and ruby silver were reported from one lode (Pardee and Schrader, 1933, p. 31).
Located in southwestern Powell County, west of Garrison, the Pioneer district includes Gold and Pikes Peak Creeks and was the site of Montana's first gold discovery along Gold Creek in 1852. Though the initial find was not rich enough to mine, sufficient interest was aroused to attract others who found more encouraging gravels along Gold Creek in 1858, 1860, and 1861. The deposits were not rich and were neglected during the frantic stampedes to other bonanza discoveries in western Montana in the 1860's.
Thus no significant development occurred until 1868-69, when a ditch 16 miles long was completed to deliver water to mine high terraces along Pikes Peak Creek (Pardee, 1951, p. 74-75). By 1871 a total of eight hydraulic giants were utilized in placer mining on Pioneer Creek and French Gulch (Lyden, 1948, p. 120), and more than $1 million in gold was recovered from terrace gravels on Pioneer Bar in the late 1870's and 1880's. By 1920 most of the favorable ground had been worked and only one large-scale hydraulic plant was active (Pardee, 1951, p. 75). About $1,350,000 worth of gold was recovered during 1933-41 from dredging operations in Pioneer Gulch. From 1942 through 1959 the district was almost inactive.
Gold production of the district through 1942 was valued at $5,667,248 (Pardee, 1951, p. 97) and included an estimate of $4 million for the period before 1897, when dependable records were not kept. Total production through 1959 was approximately 246,200 ounces.
The placers of the district, which were described in detail by Pardee (1951, p. 86-96), include creek placers, terrace or bench placers, and gold-bearing glacial drift. Some of the gold in the creek and bench placers may have been concentrated from glacial material (Lyden, 1948, p. 121).
The Pioneer district produced less than 1,000 ounces of lode gold through 1959. A small part of the district is included in the northeast corner of the Philipsburg quadrangle and is described by Emmons and Calkins (1913, p. 251). The country rock is granite of Tertiary age. The veins consist of quartz, calcite, pyrite, and chalcopyrite; some also contain a little sphalerite, galena, and gray copper. These deposits may be the source of the placer gold in the district.
The Zosell (Emery) district is located in southern Powell County on the west slope of the Continental Divide about 8 miles east-southeast of Deer Lodge. The district includes small formerly productive placer deposits and lodes valued for gold, silver, and lead.
Gold placers were discovered in the district about 1872 and during the next 20 years yielded about $75,000 (3,625 ounces) in gold (Pardee and Schrader, 1933, p. 283). There has been no placer mining in the district since 1904.
Lode mining in the Zosell district dates back to about 1888. The chief producer has been the Emery mine, though a score of mines were operated intermittently through 1951 (Robertson, 1953, p. 2-4). The production of the lodes from 1891 to 1928 was valued at about $675,000, of which about 45 percent, $303,750 (14,695 ounces), represents the value of the gold (Pardee and Schrader, 1933, p. 270). The district was most active from 1891 to 1905 and from 1935 to 1942. Total gold production through 1959 was about 39,450 ounces from lodes and 3,625 ounces from placers.
The district is underlain by andesite and basalt flows, tuffs and breccias, probably of Late Cretaceous age (Robertson, 1953, p. 5-8). On the east, just beyond the Continental Divide, these rocks are intruded by the Boulder batholith, and a few miles south of the district, an outlier of the Boulder batholith is exposed. The volcanic rocks are warped into a west-plunging syncline and offset by faults. The ore deposits are veins that have filled open spaces along fractures; locally the veins replaced the broken rock, and several feet of wallrock are mineralized.
The veins are narrow but rather persistent in length and depth (Pardee and Schrader, 1933, p. 272-283). The principal ore minerals - pyrite, arsenopyrite, sphalerite, boulangerite, tetrahedrite, chalcopyrite, and galena - are in a gangue of quartz and carbonate minerals (Robertson, 1953, p. 9-12). Oxidized ore is generally somewhat lower grade than the sulfide ore (Pardee and Schrader, 1933, p. 273).
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