By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
The gold production of Madison County is exceeded in Montana only by that of Silver Bow and Lewis and Clark Counties. Most of its gold was produced before 1904 from the placer deposits of Alder Gulch, by far the richest placers in the State. About 40 other gulches in the county produced placer gold, but only in small amounts (Lyden, 1948, p. 80-95). After 1904, lodes became increasingly important gold sources.
Most of the gold lodes and other auriferous deposits are near the contacts of Precambrian metamorphic and Paleozoic sedimentary rocks with the Tobacco Root batholith and other smaller intrusives and satellite stocks that are probably related to the Boulder batholith (Hart, in Tansley and others, 1933, p. 23-55). Some deposits are in the igneous rocks. The more productive lode areas are the Norris, Pony, Renova, Sheridan, Silver Star-Rochester, Tidal Wave, and Virginia City districts.
The total gold production of the county through 1959 was at least 3,746,000 ounces - 2,605,000 from placers and 1,141,000 from lodes. This must be considered a conservative figure, for as Lyden noted (1948, p. 80), estimates of the Alder Gulch placer production ranged from $50,612,000 to $125 million.
Located in the northeastern part of Madison County, the Norris district, which includes Norwegian, Lower Hot Springs, and Washington, has produced chiefly gold and smaller amounts of silver, copper, and lead.
Placer deposits along Norwegian Gulch and South Meadow Creek were discovered in early 1864, and Norwegian Gulch yielded $150,000 in gold by 1874 (Winchell, 1914a, p. 111). By 1902 the district had produced at least $300,000 (14,514 ounces) in placer gold (Winchell, 1914a, p. 118), and the placers were worked on a fairly large scale from 1936 through 1942.
Quartz lodes also were discovered in 1864, and within 5 years the district had at least 8 mills (Winchell, 1914a, p. 111). Production fluctuated but was almost continuous through 1953.
Winchell (1914a, p. 118) estimated that the total lode output to 1902 exceeded $3 million in combined metals. From 1902 through 1912 gold accounted for about 90 percent of the value of mine production; if the same ratio was applicable before 1902, the lode mines of the district produced about $2,700,000 (130,600 ounces) during that period. The total lode production of the district was about 235,000 ounces and the total minimum production of both lodes and placers through 1959 was about 265,000 ounces.
The geology and ore deposits were described by Winchell (1914a, p. 111-118) and by Hart (in Tansley and others, 1933).
The Norris district is on the northeast side of the Tobacco Root batholith of Late Cretaceous age. The batholith consists chiefly of quartz monzonite and is intrusive into gneiss and schist of Precambrian age. Small remnants of rhyolite and basalt of Late Cretaceous or Tertiary age intrude and cap the older rocks.
Most of the ore deposits occur in the quartz monzonite but some are in gneiss near the intrusive contact. The ore occurs in quartz veins, which are oxidized in the upper part, and contains iron oxide, gold, and silver. In the Revenue mine, the most productive in the district, the zone of oxidation extends to the 200-foot level. Some oxidized ore also carries copper carbonate and silicate minerals.
Below the zone of oxidation the most common ore mineral is auriferous pyrite, but some ore also contains galena, sphalerite, chalcopyrite, bornite, and chalcocite (Hart, in Tansley and others, 1933, p. 52).
The Pony district, which includes Mineral Hill and South Boulder (Mammoth), is in the northeastern part of Madison County in the Willow Creek drainage basin. Almost its entire output has come from lodes which have produced chiefly gold and small amounts of silver, lead, zinc, and copper. Placer gold was noted in 1870 (Lyden, 1948, p. 89), but placer production of the district has been small. Lode deposits were discovered in the early 1870's and were actively exploited during the 1880's and 1890's (Winchell, 1914a, p. 119).
Production apparently was continuous through 1918, but it declined thereafter. The district again was active from 1928 through 1944. There was no significant gold production from 1944 through 1959.
Winchell (1914a, p. 126) estimated that the mine production of the Pony district, exclusive of the South Boulder camp, through 1901 was valued at about $2,600,000. Based on production records from 1902 to 1912, it would seem reasonable that gold constituted about 90 to 95 percent of the early production or about $2,350,000 (113,690 ounces). The gold production of the South Boulder camp before 1900, all from lodes, was estimated at about $2 million (96,758 ounces) (Lyden, 1948, p. 87).
From 1902 through 1930 the district produced about 76,500 ounces (Hart, in Tansley and others, 1933, p. 24), and from 1933 through 1944, about 58,950 ounces. The total gold production of the district through 1959 was about 346,000 ounces; probably less than 250 ounces was placer gold.
Most of the mines in the Pony district are in Precambrian gneiss near the contact with quartz monzonite of the Tobacco Root batholith, but some are in the marginal part of the batholith; others are associated with aplitic and pegmatitic dikes (Winchell, 1914a, p. 119-120).
The mineral deposits in the district are arranged in a rude zonal pattern (Hart, in Tansley and others, 1933, p. 25). At or near the gneiss-quartz monzonite contact, the veins consist of either (1) chalcopyrite, pyrite, and molybdenite in quartz, (2) auriferous pyrite, chalcopyrite, and quartz, or (3) tungsten-fluorite minerals. Galena and silver are the important vein constituents peripheral to these deposits, and auriferous pyrite is less abundant.
In the Clipper mine, the most productive in the district, and in the adjacent Boss Tweed mine, the ore deposits consist mostly of silicified and pyritized gneiss between two approximately parallel faults from 10 to 160 feet apart (Winchell, 1914a, p. 121-124). Some of the ore is oxidized. The economic deposits are found chiefly in shoots, but much of the gneiss between the faults contains gold.
The Renova district, which includes Bone Basin, is located in northern Madison County in the north end of the Tobacco Root Mountains. The district produced chiefly gold and some silver, most of which came from the Mayflower mine. The date of discovery of ore in the district is not known, but there was little mining activity until 1896 when the Mayflower ore body was discovered, after which the region became prominent (Winchell, 1914a, p. 97).
The Mayflower mine closed in 1905, and other mines in the district operated only intermittently and on a small scale through 1912. The district again became active during the early 1930's; the Mayflower mine was reopened in July 1935 and again became the chief producer. The district reached a peak production of 21,539 ounces of gold in 1940, but activity declined sharply after 1942 and no production was recorded from 1953 through 1959.
Production prior to 1896 was probably of little significance. From 1896 through 1912 the district produced 60,023 ounces of gold valued at $1,282,052; most of this was from the Mayflower mine and was produced before 1905 (Winchell, 1914a, p. 101). From 1932 through 1953 production was 102,036 ounces, or a total of about 162,000 ounces.
The geology and ore deposits of the Renova district were briefly described by Winchell (1914a, p. 99-101). The oldest rocks are arkosic sandstone, sandy shale, and slate of the Belt Series of Precambrian age. These are overlain by rocks of Cambrian age and possibly younger rocks, consisting, in ascending order, of a basal conglomerate, quartzite, and shale, and limestone. Dikes of andesite and quartz porphyry cut the sedimentary rock.
The Mayflower ore, consisting chiefly of telluride minerals, is along a bedding fault in limestone. The ore above the 300-foot level was oxidized.
The ore in the other mines of the district is in veins that cut rock of the Belt Series. This ore is oxidized and contains free gold in iron oxide and quartz. The unoxidized ore consists of pyrite, chalcopyrite, and galena in a gangue of calcite, dolomite, and siderite.
Located in the western part of Madison County 10 to 12 miles northeast of Virginia City, the Sheridan district, which includes Ramshorn, is important chiefly for gold, but silver, copper, and lead have also been recovered. Small amounts of gold have been mined from placers. Quartz veins were discovered in 1864 (Winchell, 1914a, p. 133), and mills were erected as early as 1865. The district was a steady producer through about 1952, although output dropped sharply after 1948. No activity was reported in 1959.
Production data for 1864-1904 are not available (Winchell, 1914a, p. 139); however, several mines are known to have produced more during that period than after 1904. The total gold production from 1905 through 1952 was about 33,500 ounces, of which about 2,100 ounces was from placers.
The Sheridan district is underlain by Precambrian schist and gneiss interbedded with quartzites and limestones. These rocks are intruded by small stocks of quartz monzonite and dikes and sills of porphyry of Late Cretaceous or Tertiary age (Winchell, 1914a, p. 133-139; Hart, in Tansley and others, 1933, p. 40-45).
The ore deposits are veins and limestone replacement deposits in the Precambrian rocks. The chief sulfide minerals are pyrite, arsenopyrite, chalcopyrite, galena, and tetrahedrite in a gangue of quartz and small amounts of siderite. The gold occurs with the pyrite. Tellurides are not common but have been reported in the Indian Creek area (Hart, in Tansley and others, 1933, p. 41). Much of the ore was oxidized and consisted of gold in hematite with some copper oxides and carbonate.
SILVER STAR-ROCHESTER DISTRICT
Located in northwestern Madison County, west of the Jefferson River, the Silver Star-Rochester district produced ores that were valuable chiefly for gold, but silver, lead, zinc, and copper also were recovered. Though mining began in the 1860's, it did not reach its peak until 1935-42. Interest declined thereafter, and the district was virtually dormant from 1951 through 1959.
The Watseca mine in the Rochester area and the Green Campbell, Iron Rod, and Broadway mines in the Silver Star area were the major mines of the district.
Incomplete records indicate that the gold output through 1903 was worth about $2 million (about 97,000 ounces) (Sahinen, 1939, p. 5-7; Winchell, 1914a, p. 144). Total production through 1959 was about 185,700 ounces, all from lodes.
The geology and ore deposits of the district were briefly described by Winchell (1914a, p. 126-132; 139-144) and Sahinen (1939), from which this summary is abstracted.
The Silver Star-Rochester district lies at the south end of the Boulder batholith. The bedrock consists dominantly of schist and gneiss of Precambrian age which in the western part of the district and in the area around Silver Star are locally overlain by sedimentary rocks that range in age from late Precambrian to Pennsylvanian.
All the older rocks are intruded by quartz monzonite of the Boulder batholith, by a stock of diorite, by small aplite intrusive bodies, and by dikes and sills of acidic rocks, all of Cretaceous or Tertiary age. Remnants of andesite and basalt flows are found locally.
The most important ore deposits are northeast-trending veins in gneiss and schist (Sahinen, 1939, p. 26-34). These veins are rich in gold and silver and contain arsenopyrite, pyrite, and subordinate amounts of lead, zinc, and copper minerals in a quartz gangue. A few veins in this group are rich in lead-silver ore. Several narrow veins that trend east carry gold with small amounts of pyrite in greasy-appearing quartz. Much of the ore has been oxidized to a depth of 600 feet and consists of quartz, limonite, and oxidized copper and lead minerals.
Considerable gold has been mined from contact deposits in the Silver Star area. The ore deposits form irregular shoots in Paleozoic limestone along the quartz monzonite contact. Much of the ore was highly oxidized and consisted of jasper, gold, and oxidized minerals of iron and copper. The unoxidized ore consists of pyrite, chalcopyrite, bornite, and covellite in a gangue of quartz and contact silicate minerals.
TIDAL WAVE DISTRICT
Located in northwestern Madison County, along the western slope of the Tobacco Root Mountains, the Tidal Wave (Twin Bridges) district has produced chiefly gold, silver, and lead, and smaller amounts of copper. The initial discoveries in about 1864 were silver-lead ore but these aroused little excitement. Only gold was sought in those early days. By 1874, however, the value of the argentiferous lead ores was realized, and claims were rapidly located and developed (Winchell, 1914a, p. 145).
Production records date back only to 1904, but the production during the latter part of the 19th century probably was greater than in the early 1900's (Winchell, 1914a, p. 146). The district remained active from 1904 through 1955, and the total recorded gold production through 1959 was about 33,400 ounces; nearly all production was from lodes.
The Tidal Wave district lies on the west side of the Tobacco Root batholith, a mass of quartz monzonite of Cretaceous or Tertiary age which here has intruded, faulted, and tilted Precambrian gneiss and schist and Paleozoic limestone, quartzite, and interbedded shale. These rocks also are cut locally by sills of porphyry and by aplite dikes.
The ore deposits in the district are contact deposits in limestone and lodes in gneiss and schist, and more rarely they occur in the quartz monzonite near its contact with the country rocks. Most of the veins contain gold and lesser amounts of lead, silver, copper, and zinc. A few veins in the Paleozoic limestone near the contact were mined for lead and silver, or copper and gold. The contact metamorphic deposits are valued mainly for copper and lead, with silver and gold as minor constituents (Winchell, 1914a, p. 145-158; Hart, in Tansley and others, 1933, p. 34-39).
VIRGINIA CITY-ALDER GULCH DISTRICT
The Virginia City-Alder Gulch district, which includes the Summit area, is in central Madison County at the south end of the Tobacco Root Mountains. It is the leading producer of placer gold in Montana and has also produced a small amount of lode gold. The discovery of rich gold placer deposits in Alder Gulch in 1863 marked the beginning of mining activity in Madison County. Gold-quartz veins were discovered in the district later in the year (Winchell, 1914a, p. 159).
The richness of the placers attracted hordes of prospectors to the area, and within 18 months Virginia City boomed to a town of 10,000 population. Within 3 years, placer gold valued at $30 million was recovered from Alder Gulch and its tributaries (Knopf, 1913, p. 15). The Alder Creek placers, extending for about 20 miles, were the longest and most productive ever discovered in Montana. From 1863 until 1899 the gravels were worked by sluice boxes, pans, and rockers.
In 1899 the Conrey Placer Mining Co. began dredging operations that lasted until 1922, when the gravels were considered mined out. The peak year of dredging, 1915, resulted in more than $800,000 in gold recovered from 6 million cubic yards of gravel (Lyden, 1948, p. 80-82).
During the 14 years following 1922 only small-scale sluicing operations were undertaken. In 1935 dryland dredges were installed (Lyden, 1948, p. 82) and were successfully operated through 1942, when operations closed for the duration of World War II. Dredging was resumed in 1946 but was suspended in late 1948.
The gold-bearing gravel in Alder Gulch is 30 to 50 feet deep; the most valuable gravel is about 6 feet above the soft, plastic bedrock (Kirk, 1908, p. 330). The placer gold probably was weathered directly from the thousands of veins of the district (Lyden, 1948, p. 83).
Various estimates have been made regarding production of the Alder Gulch placers before 1904. In addition to the $30 million produced during the first 3 years (1863-66), Hart (in Tansley and others, 1933, p. 46) estimated that Alder Gulch and its tributaries yielded $42.75 million from 1867 through 1903. The Montana Bureau of Agriculture, Labor,and Industry (1900, p. 188) estimated production at $150 to $200 million in gold through 1899. Kirk (1908, p. 330) estimated the output by 1908 at $125 million. Lyden (1948, p. 80) believed that Hart's estimate was low and Kirk's was high.
Almost certainly Hart's figure of $42.75 million (2,068,215 ounces) is a conservative estimate for the period 1863-1903. From 1904 through 1930 the production was 380,351 ounces (Hart, in Transley and others, 1933, p. 46), and from 1932 through 1959, about 24,500 ounces. Therefore the total production through 1959 was at least 2,475,000 ounces.
Lodes also were productive in the Virginia City district. The first lode deposits were developed soon after 1864, and by 1871 at least 8 mills had been erected to treat the gold-quartz ores (Winchell, 1914a, p. 159). Much of the early lode production came from the Oro Cache and Kearsarge mines, in the Summit camp, which produced an estimated $500,000 and $150,000 in gold, respectively by 1881 (Winchell, 1914a, p. 159). Hart (in Tansley and others, 1933, p. 46) estimated the lode production during 1867-90 at $1 million (48,379 ounces), and during 1891-1903, at $269,256 (13,026 ounces).
Lode production fluctuated but continued at a moderate scale through 1914 and ranged from $131,000 in 1910 to only $12,856 in 1912 (Hart, in Tansley and others, 1933, p. 46). Thereafter, production was sporadic and it declined sharply until the price of gold was raised in 1934. Annual production after 1934, except during World War II, ranged from about 1,300 to 4,500 ounces. Very small amounts of lode gold were mined in the 1950's. Total lode production of the district was about 142,000 ounces, and the minimum total placer and lode production through 1959 was about 2,617,000 ounces.
The following brief summary of the geology and ore deposits has been abstracted from reports by Winchell (1914a, p. 159-165) and Hart (in Tansley and others, 1933, p. 47-50).
The district is underlain by gneiss and schist of Precambrian age and intrusions of aplite and andesite porphyry of Cretaceous or Tertiary age. East of Virginia City the uplands are capped by basalt flows of Tertiary age. The lode deposits are chiefly in the gneiss and schist, but one vein system is in aplite. The lodes are quartz veins and stringers that contain auriferous pyrite, galena, sphalerite, and chalcopyrite and lesser amounts of gold tellurides, tetrahedrite, argentite, and stibnite.
Most of the ore shipped was oxidized and consisted of gold and free silver in quartz, iron oxides, manganese oxides, and a little locally occurring copper stain.