By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
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Broadwater County, in west-central Montana, was noted for its gold placers, which were among the most productive in the State. Though production before 1904 was not recorded, it was large. The estimated placer gold production of Confederate Gulch alone was about $12 million (580,550 ounces) (Pardee and Schrader, 1933, p. 172-173), and significant production has also come from placers along White, Avalanche, Beaver, Indian, and Crow Creeks (Lyden, 1948, p. 17-20).
Early lode production is also unrecorded, but it probably was small. Total gold production for the county from 1901 through 1959 was approximately 362,000 ounces - about 327,500 ounces from lodes and 34,500 ounces from placers; from the beginning of mining through 1959 the total probably was about 1 million ounces.
CONFEDERATE GULCH DISTRICT
The Confederate Gulch (Backer) district is along Confederate Gulch, a tributary of the Missouri River in northern Broad water County, about 11 miles north of Townsend. Gold has been mined chiefly from placer deposits along Confederate Gulch and its tributaries; only a little production has come from lode deposits. The placers along Confederate Gulch were discovered in 1864 and proved to be exceedingly rich; they were higher in grade, though lower in tonnage, than the well-known placers along Alder Gulch in Madison County and along Last Chance Gulch in Lewis and Clark County.
The total yield is estimated to be worth about $12 million (580,550 ounces), most of which was achieved in the first 5 years of mining. After 1869 placer mining declined rapidly and by 1880 only a few miners remained in the district (Pardee and Schrader, 1933, p. 171-173). Lode production in the early years was of little consequence, but from 1908 through 1951 lodes were worked continuously on a small scale, except during World War II. No activity was reported in either lodes or placers from 1953 through 1959.
The total gold production of the district through 1959 was "between 550,000 and 600,000 ounces; all but about 10,000 ounces was from placers.
The placers are in stream terrace gravels believed to be Pleistocene in age (Pardee and Schrader, 1933, p. 174-175). They were deposited at several levels by streams during the process of excavating the Confederate Gulch drainage basin. Pardee concluded that the distribution of the gold-bearing gravel indicates that the chief, if not the only, source of the gold is the quartz lodes on Miller Mountain at the head of Montana Gulch.
Most of the district is underlain by Precambrian shaly, slaty, and calcareous rocks of the Belt Series. These are disconformably overlain by Paleozoic sedimentary rocks that include the Flathead Quartzite, Wolsey Shale, and unnamed limestone and shale, all of Cambrian age; limestone and shale of Devonian age; and the Madison Limestone, Quadrant Quartzite, and Phosphoria Formation, all of Carboniferous age.
These rocks were folded into a large northwest-trending anticline, exposing the Precambrian rocks in the eastern part of the district and steeply dipping bands of Paleozoic rocks in the western part. The rocks were also cut by prominent thrust faults and were intruded during Late Cretaceous or early Tertiary time by sills, dikes, and small stocks of quartz diorite and quartz monzonite (Pardee and Schrader, 1933, p. 123-132). Gold-quartz veins are along fractures in the quartz diorite and bedding planes in adjacent Precambrian shale.
A few lodes are replacement bodies in the quartz diorite. Quartz, pyrite, and galena are characteristic minerals of both types of lodes. The oxidized parts of the deposits contained quartz, iron oxides, and small specks of native gold (Pardee and Schrader, 1933, p. 139-146).
PARK DISTRICT
The Park (Indian Creek, Hassel) district, on the east side of the Elkhorn Mountains between Winston and Radersburg, has produced lode and placer gold, silver, and a little lead and zinc. Placer deposits were discovered about 1860 along Indian Creek near Hassel, and gold veins were discovered later (Stone, 1911, p. 90). The placers yielded about $50,000 (2,370 ounces) in 1871, but little else is known of the early placer operations (Lyden, 1948, p. 19). There was placer mining in 1911-15, 1933-43, and again in 1945-49.
Records of the early lode mining are meager. According to Stone (1911, p. 90), tunnels and open-pit mining along some large mineralized zones produced about $500,000 (23,690 ounces) in gold, probably prior to 1908. With few exceptions there was some production every year from 1908 through 1957. The district was idle from 1957 through 1959.
M. R. Klepper (written commun., 1962) summarized gold production as follows: 1864-1904, $850,000; 1905-28, $50,000; 1929-56, $1,250,000. Production from 1864 to 1904 was mainly from placers and from some lode mines in the Hassel area. From 1929 to 1956, production was mainly lode gold from the Marietta mine. Total production for all three periods was about 80,300 ounces of gold valued at $2,150,000.
Most of the lode deposits in the Park district are quartz veins in andesite which is intruded by quartz monzonite. The ore consists chiefly of auriferous pyrite accompanied by arsenopyrite and galena; the principal value is in gold (Stone, 1911, p. 89-91).
RADERSBURG DISTRICT
The Radersburg (Cedar Plains, Crow Creek) district, on the east side of the Elkhorn Mountains in southern Broadwater County, was the largest producer of lode gold in the county; it also produced some placer gold and significant amounts of silver, copper, lead, and a small amount of zinc.
Placer and lode deposits were discovered in 1866 (Winchell, 1914a, p. 173, 182). By the late 1870's the easily worked oxidized gold ores were depleted, and most of the mines closed. In 1883 railroad connections were made with the large smelters at Butte and Helena that treated sulfide ores at low costs. The mines at Radersburg were reactivated and continued in operation through 1956. The district was idle from 1956 through 1959.
Placer deposits are found for several miles along Crow Creek and Johnny Gulch near Radersburg. Old residents of the district estimated the placer production from 1866 to 1904 at $500,000 (24,380 ounces) to $1 million (48,379 ounces) (Winchell, 1914a, p. 182). Placer production after 1904 was about 850 ounces. The total gold production of the district through 1959, including both lode and placer, was about 325,000 ounces.
The principal gold deposits in the Radersburg district are in veins in andesitic volcanic rocks and associated intrusive diorite porphyry of Late Cretaceous age (M. R. Klepper, written commun., 1962). A stock of monzonite cuts these rocks about a mile south of the major mines. Ore deposits, which are valued mainly for silver, lead, and zinc, are along or near contacts of intrusive rocks with Paleozoic and Mesozoic sedimentary rocks.
The most valuable deposits are gold-bearing pyrite veins containing a very small amount of chalcopyrite and very little quartz or other gangue material. A few veins contain quartz and small amounts of sphalerite, arsenopyrite, chalcopyrite, and galena. The ore along or near the igneous contacts is accompanied locally by calcite, siderite or ankerite, limonite, and pyrolusite. Cerussite, wulfenite, and hematite are in the oxidized parts of a few deposits.
WHITE CREEK DISTRICT
The White Creek district, in northern Broadwater County northwest of Confederate Gulch, includes the drainage basins of White Creek, Avalanche Creek, and upper Magpie Gulch, all of which are tributaries of the Missouri River. Production of the district consists chiefly of placer gold and a small amount of lode copper. Gold was discovered in the gravel along White Creek in 1865, and the placers along the upper part of White Creek and Johnny Gulch, a tributary, were mined for about 20 years (Pardee and Schrader, 1933, p. 179). The deposits were rich but production data are not available.
Johnny Gulch was mined for a mile or more, and below its mouth in White Creek, drift mining was undertaken for a mile or more. Based on the amount of gravel moved, Pardee (in Pardee and Schrader, 1933, p. 179) estimated the yield at about $1 to $1.5 million worth of gold. The Avalanche Creek placers yielded at least $100,000 and Magpie Gulch yielded about $330,000 in gold (Lyden, 1948, p. 18, 73). Most of the production was before 1904; only a few ounces was reported in the 1920's and 1930's from desultory diggings along White Creek and Magpie Gulch. Total gold production through 1959 was between 68,000 and 92,000 ounces.
The country rock of the White Creek district is almost the same as in the Confederate Gulch district and consists of folded and faulted Precambrian and Paleozoic sedimentary rocks and intrusive diorite and quartz diorite, chiefly dikes, of Cretaceous or Tertiary age (Pardee and Schrader, 1933, p. 15). The placer gold along White Creek was derived from the same gold quartz veins on Miller Mountain that supplied the gold of Confederate Creek (Pardee and Schrader, 1933, p. 162-163, 174, 179).
The source of the placer gold in Magpie Gulch and its tributaries and in Avalanche Gulch is considered to be the quartz veins that are associated with diorite dikes in the area. (Lyden, 1948, p. 74; Pardee and Schrader, 1933, p. 179).
WINSTON DISTRICT
The Winston (Beaver Creek) mining district is in north Broadwater County in the drainage basin of Beaver Creek, a tributary of the Missouri River. Production of the district has come chiefly from lode mining of gold and mixed sulfide ores; placer gold mining, which began about 1866, has been relatively unimportant. According to Lyden (1948, p. 19), there is no record of placer mining since 1915.
The first lode was discovered in 1867 on the East Pacific property; there were other early discoveries, but apparently little mining was done until 10 to 20 years later (Pardee and Schrader, 1933, p. 211-212, 216). After 1900 the greatest activity was during 1908-18 and 1926-53. The district was idle from 1953 through 1959.
Early production records are fragmentary, but the production of precious and base metals through 1928 was estimated to be at least $3 million, of which about $2 million was mined before 1908 (Pardee and Schrader, 1933, p. 212). Though the amount of gold was not stated, it must have been a major constituent, especially of those ores that were oxidized. Total gold production through 1959 was worth about $2,750,000, of which 90 percent was from lodes and 10 percent from placers (M. R. Klepper, written commun., 1962). This amounts to roughly 106,000 ounces from lodes and 12,000 ounces from placers.
In the Winston district (Stone, 1911, pi. 3), small stocks of quartz monzonite of probable Late Cretaceous age intrude a thick sequence of andesite flows, tuffs, and breccias of Late Cretaceous age (M. R. Klepper, oral commun., 1962). The ore deposits are in quartz veins in the andesite and in quartz monzonite. The ore minerals are pyrite and locally occurring galena, sphalerite, chalcopyrite, or their oxidation products.
Arsenopyrite and tetrahedrite are rare components (Pardee and Schrader, 1933, p. 214). Gold occurs in all the veins and is the main valuable constituent in oxidized ores; it is relatively less abundant in unoxidized ores, where it is associated with the sulfide minerals.
