By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
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From 1864, when gold was discovered in the county, through 1959, Jefferson County produced at least 700,000 ounces of gold - about 575,000 ounces from lodes and about 125,000 ounces from placers.
Mining began in Jefferson County in about 1864 with the discovery of silver, lead, and gold ore near Wickes (Pardee and Schrader, 1933, p. 232-234) and has continued at a fluctuating rate to the present time. Gold mining declined during the late 1920's, increased after the price of gold was raised in 1934, and again declined sharply in 1950.
Most of the deposits, both lode and placer, are in the northern part of the county. The most productive placer deposits have been the gravels along Prickly Pear Creek and its tributaries in the Clancy district, about 14 miles southeast of Helena, but small production has also come from placers in the Basin and Boulder district. The output of lode gold has come chiefly from the Clancy, Basin and Boulder, Elkhorn, and Whitehall districts.
Some of the ore deposits are in granitic rocks of the Boulder batholith, and some are in sedimentary and volcanic wallrocks and roofrocks near the contact with the batholith.
BASIN AND BOULDER DISTRICT
In the Basin and Boulder district, in central Jefferson County near the headwaters of Boulder River, gold has been recovered from gold lodes, from silver and base metal ores, and from placers. The district includes Basin Creek, Cataract Creek, Lowland Creek, and the upper Boulder River.
Lodes were discovered in this area before 1870, but mining has been sporadic (Pardee and Schrader, 1933, p. 286). The periods of peak activity were 1905-8, 1916-20, 1924-26, and 1935-41. From the end of World War II through 1954 activity was on a small scale, and from 1954 through 1959, no production was recorded. Relatively small amounts of gold were mined from gravels along Lowland Creek, Basin Creek, Cataract Creek, and Boulder River (Lyden, 1948, p. 48-50).
Total gold production of the district through 1959 was about 188,200 ounces, about two-thirds of which was produced before 1928 (Pardee and Schrader, 1933, p. 186). About 12,000 ounces of gold from placers is included in the total figure.
Bedrock in the Basin and Boulder district is predominantly quartz monzonite of the Boulder batholith and remnants of older andesitic flows of Late Cretaceous age that were intruded by the quartz monzonite. Patches of dacite flows of Tertiary age unconformably overlie the quartz monzonite. Dikes of dacite and rhyolite cut all these rocks (Pardee and Schrader, 1933, p. 286-287).
The ore deposits are of at least two ages. The principal group of lodes is older than the Tertiary volcanics and is valuable for silver, lead, gold, zinc, and copper. Younger lodes in Tertiary volcanics are found in a small area along Lowland Creek. These are epithermal veins and are mined for gold and silver (M. R. Klepper, written commun., 1962).
Billingsley and Grimes (1918, p. 313) noted a tendency toward mineral zoning in veins near Basin. Veins in the upper part of the batholith and in the roofrocks contain quartz, tourmaline, and arsenopyrite. Underneath this zone, from 200 to 500 feet below the roof of the batholith, galena predominates but gives way downward to sphalerite. The deepest ore is the lowest in grade and contains pyrite and copper minerals.
CLANCY DISTRICT
The Clancy district is in the northern part of the county, about 10 miles south of Helena. Though primarily a placer district, most of the gold produced in the district before 1900 was a byproduct of flourishing silver mines.
Placer mining began about 1865 along Prickly Pear Creek and the following year rich silver lodes were found. By 1910, however, most of the mines were idle, and the once-thriving town of Lump Gulch City was deserted (Pardee and Schrader, 1933, p. 227). In 1933 a dredge was installed on Prickly Pear Creek. In 1937 and 1938 additional large-scale operations, which resulted in considerable placer production through 1948, were undertaken on Prickly Pear and Clancy Creeks.
From 1949 through 1957 the placer operations were suspended. In 1958 and 1959 placers were again mined on Prickly Pear Creek, but production data were not recorded.
Total gold production of the district through 1959 was about 101,000 ounces from placers and at least 2,000 ounces from lodes.
The predominant bedrock in the district is quartz monzonite and is part of the Boulder batholith of Late Cretaceous or Tertiary age. Remnants of a once-extensive cover of Tertiary rhyolite occur in the eastern and northeastern parts of the district. The lode deposits are in veins in quartz monzonite.
The richest deposits contained silver-bearing galena, sphalerite, and tetrahedrite in a chalcedonic quartz gangue. Other veins produced small amounts of gold. These consisted mainly of quartz and pyrite, and small amounts of galena, sphalerite, and arseno-pyrite (Knopf, 1913, p. 102-104).
ELKHORN DISTRICT
Located in the Elkhorn Mountains east of Boulder, the Elkhorn district was prospected before 1870, but the highly productive Holter lode in the Elkhorn mine was not discovered until 1875. The early economic importance of this district depended almost wholly on the Elkhorn mine (Knopf, 1913, p. 128) which produced mostly silver and lead ore and small amounts of byproduct gold.
After 1911 as many as 16 mines operated in a single year, but the bulk of the more recent production came from the Golden Curry and Swissmont mines and the reworked tailings of the Elkhorn mine (Pardee and Schrader, 1933, p. 299-300). The total gold production of the district through 1953 was 70,015 ounces (Klepper and others, 1957, p. 64). From 1954 through 1959 only 97 ounces was recorded.
The Elkhorn district lies on the eastern margin of the Boulder batholith. The oldest rock in the district is metamorphosed shale of the Belt Series which is overlain by metamorphosed Paleozoic limestone, shale, and quartzite, ranging in age from Cambrian to Pennsylvanian, and by Mesozoic sandstone, shale, and impure limestone. These are overlain by a bedded series of andesitic breccias, tuffs, and lavas of Late Cretaceous age.
The sedimentary and volcanic rocks are folded, faulted, and cut by small igneous masses of diverse composition that are slightly older than the Boulder batholith, by quartz monzonite of the batholith, and by aplite (M. R. Klepper, written commun., 1962).
A wide variety of ore deposits is found within the Elkorn district: magmatic sulfide deposits at the Golden Curry property, auriferous contact metamorphic deposits in the Dolcoath mine, auriferous lead-silver replacement deposits at the Elkhorn mine, and mineralized breccia pipes at the Elkhorn Queen and Skyline mines (Klepper and others, 1957, p. 64). Magmatic sulfide ore consists of a mixture of pyrrhotite and chalcopyrite intergrown with augite.
The contact ore body in the Dolcoath mine consists of chalcopyrite and an auriferous sulfide and telluride of bismuth intergrown with silicates and calcite. The ore at the Elkhorn mine consists mainly of argentiferous galena, sphalerite, pyrite, and tetrahedrite as replacement bodies in dolomite beneath hornstone. At the Elkhorn Queen and Skyline mines pipelike bodies of brecciated rock are cemented by quartz, black tourmaline, pyrite, galena, sphalerite, and sparse chalcopyrite and arsenopyrite (Klepper and others, 1957, p. 64).
TIZER DISTRICT
The Tizer (Wilson Creek) district is about 20 miles southeast of Helena, immediately northeast of the Elkhorn district.
Two lode mines in this district - the Callahan and Center Reef - have produced a total of 9,536 ounces of gold (Klepper and others, 1957, p. 72-73). Klepper (written commun., 1962) estimated that other lodes in this district produced about 500 ounces of gold and that placers along Wilson and Crow Creeks produced between 500 and 1,000 ounces - a total of roughly 10,500 ounces. The Callahan property was productive as recently as 1951, but no activity was reported from 1952 through 1959.
At the Callahan mine, the ore deposits are in narrow veins in andesitic extrusive rocks of Late Cretaceous age. The veins, which are as much as 6 feet thick, consist of pyritic andesite and quartz with sparse pyrite, galena, sphalerite, chalcopyrite, and specks of gold and tetrahedrite(?).
The country rock at the Center Reef mine is similar to that at the Callahan. The ore is in a narrow vein with mineralogy similar to that of the Callahan deposit (Klepper and others, 1957, p. 72-73).
WHITEHALL DISTRICT
Located on the south end of Bull Mountain in the south-central part of the county, the Whitehall (Cardwell) district has produced lode gold, silver, and lead.
The chief mine, the Golden Sunlight, was opened in 1890 and was operated almost continuously until 1957 (Roby and others, 1960, p. 82-83). Roughly three-quarters of the recorded gold production of 71,850 ounces between 1902 and 1957 came from this mine. Production of the Golden Sunlight from 1890 to 1910 was $1.5 million in gold and silver (Roby and others, 1960, p. 83). Total gold production of the district through 1959 was at least 100,000 ounces.
The rocks of the district are shales, sandstones, and sandy limestones of the Precambrian Belt Series conformably overlain by a thick sequence of Paleozoic rocks, mainly limestone. The sedimentary rocks are intruded by quartz porphyry, andesite, and basalt dikes. The ore occurs in veins in the sedimentary rocks and in the porphyry. The ore contains auriferous pyrite, galena, and sphalerite in a quartz gangue (Winchell, 1914a, p. 97-99).
WICKES DISTRICT
In the Wickes (Colorado) district, in north Jefferson County, about 20 miles south of Helena, gold has been a byproduct of rich silver-lead ores.
Lode mining began in 1864 with the discovery of the Gregory lode. Four mines - the Gregory, Alta, Comet, and Minah - have been the sources of nearly all the metals produced in the district. The most active period was from 1880 to 1893; however, the district was active almost continuously through 1959.
Gold production from 1864 to 1928 was estimated at $4,325,000 (about 210,000 ounces) from lodes and $25,000 (about 1,200 ounces) from placers (Pardee and Schrader, 1933, p. 186). Total production through 1959 was roughly 264,000 ounces from lodes and 2,200 ounces from placers.
The oldest rocks in the district are andesites and latites of Cretaceous age, which occur as roof remnants in quartz monzonite of the Boulder batholith. The quartz monzonite is intruded by large masses of aplite.
The ore deposits are in quartz veins in altered andesite or sericitized quartz monzonite or aplite. The principal ore minerals are galena, sphalerite, pyrite, chalcopyrite, tetrahedrite, and arsenopyrite. In the oxidized zone are cerussite, anglesite, bournonite, and covellite. Tourmaline is abundant in the wallrock and in the veins (Pardee and Schrader, 1933, p.234-235).
