The Lincoln district includes Lincoln Gulch and several other tributaries of the Blackfoot River near the town of Lincoln in the western part of Lewis and Clark County. Most of the gold mined in the district was from placer deposits; a small amount was from lodes. The gold placers, which were discovered about 1865, were rich and hastily worked, and by about the middle 1870's the camp was virtually abandoned (Pardee and Schrader, 1933, p. 115-117). Pardee and Schrader (1933) estimated that during these early years a stretch of the gulch 7,400 feet long yielded about $7 million (338,653 ounces) in gold. The placers were worked intermittently from 1904 through about 1955 and yielded at least 2,700 ounces of gold. The total placer production through 1959 was about 342,000 ounces.
Lode production, which probably totaled less than 200 ounces, was mined sporadically, mostly during the 1930's.
Low-grade gold ore, which averages $2.20 to $3 per ton, is found in a diorite dike that has intruded calcic argillite of the Belt Series (Pardee and Schrader, 1933, p. 116-117). The lode follows a shear zone and is as much as 30 feet wide. The diorite in the shear zone is largely replaced by quartz, siderite, and pyrite.
All production of the McClellan district, which is in the western part of Lewis and Clark County about 8 miles south of Lincoln, has been placer gold. Placer mining in McClellan Gulch dates back to 1864, and by 1875 these deposits yielded an estimated $7 million (338,653 ounces) in gold (Pardee and Schrader, 1933, p. 117). The gravels were very rich and have been reworked in places as many as two or three times since 1875. The amount of gold recovered since 1875 is not known. The total minimum production of these placers through 1959 was about 340,000 ounces. About 10 ounces of lode gold was produced in the late 1940's.
The source of the gold probably was the low-grade gold-quartz lodes that crop out on the slopes at the head of the gulch (Pardee and Schrader, 1933, p. 118).
MARYSVILLE-SILVER CREEK DISTRICT
The Marysville-Silver Creek (Ottawa) district, near the headwaters of Silver Creek about 18 miles northwest of Helena, also includes the Bald Butte area. The district has been one of the most productive precious-metal mining districts in Montana. Most of the gold has come from veins, although a smaller amount has come from placer deposits. Some mines have also produced substantial amounts of lead.
The first placer mining in the district was along Silver Creek in 1864, and these placers accounted for at least 75 percent of the placer production of the district (Lyden, 1948, p. 60). The placers were rich and were mined out in the early years; in fact, no placer activity was reported in the district from 1904 to 1933 (Lyden, 1948, p. 60). From 1938 to 1941, dredging and dragline shovel operations were undertaken.
The placer production during the early period was estimated at about $3,200,000 (154,813 ounces) (Lyden, 1948, p. 60), and the total through 1959 was about 164,500 ounces.
Lode mining dates back to 1876 and the discovery of the rich Drumlummon lode, the most productive and most steadily mined lode in the district (Knopf, 1913, p. 61-62). In the early 1890's, the Drumlummon property became involved in protracted litigation and the mine was worked only intermittently. In 1911 the mine was sold, and the new owners rehabilitated both the milling plant and mine and began exploration for new ore bodies. In later years tailings from the Drumlummon mill were also reworked (Pardee and Schrader, 1933, p. 63). The last significant lode gold production was reported in 1951. The lode production of the district before 1903 was valued at about $30 million in gold and silver (Knopf, 1913, p. 62), of which possibly 60 percent was in gold. About half of the early production was from the Drumlummon mine. Total lode gold production through 1959 was about 1,145,800 ounces. If placer production is included, the district had a total yield through 1959 of about 1,310,-000 ounces.
The Marysville-Silver Creek district is centered around a small stock of quartz diorite of Late Cretaceous or Tertiary age that has intruded limestone and shale of the Belt Series of Precambrian age (Barrell, 1907, p. 7-19). The sedimentary rocks adjacent to the stock have been metamorphosed to a hard and dense-textured hornstone locally called slate, in a zone ranging from 1/2 to 2 miles in width. Numerous dikes of pegmatite, aplite, and diorite porphyry cut the stock and the sedimentary rocks.
The ore deposits are steeply dipping gold and silver veins around the border of the quartz diorite stock. Some veins are in the marginal part of the diorite, but most are in metamorphosed sedimentary rocks. The gold is finely divided and accompanies the ore minerals tetrahedrite, chalcopyrite, pyrite, sphalerite, and galena. The gangue minerals are chiefly lamellar quartz and calcite (Knopf, 1913, p. 64-66); the calcite contains some iron and manganese.
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