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).
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