The Hellgate district is located on the western slope of the Big Belt Mountains between Helena and White Sulphur Springs. Despite its proximity to the rich Confederate Gulch district, Hellgate gravels yielded no placer returns and only one lode mine proved profitable. The Argo mine produced copper sporadically from the early 1900's until its closure in the late 1920's (Lyden 1948; Pardee and Schrader 1933; Reed 1951).

The underlying rocks of the Hellgate district are primarily shales and limestones of the Spokane, Greyson, Helena, and Newland formations. The diorite and quartz diorite dikes that cut through these rocks are associated with the significant ore bodies. Gold lodes, located in the northern portion of the district, are narrow quartz veins found in association with the diorite. In contrast, copper lodes, found in the southern part of the district, occur in fissures in the shale. Chalcopyrite, ankerite and quartz are the primary minerals in the Hellgate district (Sahinen 1935).

At least three companies operated the Argo mine during its peak years: Eclipse-Argo Company from 1902-1909, Castleton Copper Company from 1916-1917, and Furnace Creek Oxide Copper Company from 1917- 1918. Total production during this time was just under three million pounds of copper, with net smelter returns amounting to $500,974 (Pardee and Schrader 1933).

Avalanche Creek Sub-district

The Avalanche Creek subdistrict is located in a parallel drainage set between Hellgate Gulch to the northwest and White Creek to the southeast. The area is noted for a small amount of placer mining near the mouth of Thompson Gulch (Lyden 1948).

The source of the placer gold found along Avalanche Creek appears to be a diorite dike and associated quartz vein seen in the Golden Messenger group more than 10 miles to the west. In addition, the mantle in the area above the outlet of Cayuse Gulch contains "float vein rock of calcite and quartz" (Lyden 1948).

Miners worked the placer grounds along Avalanche Creek for a mile on either side of the mouth of Thompson Gulch, 13 miles up from the mouth of the main drainage. The gravels yielded close to $100,000 in gold, with no production reported after 1904. Mike Finch followed the gulch in an attempt to find the source of the placer gold, and in 1903 he worked to develop a 16-foot lead of free milling gold at the head of Avalanche Creek. He reported that the ore had a value of $18 per ton (Lyden 1948; Western Mining World, 21 February 1903).

Magpie Gulch Sub-district

The Magpie Gulch sub-district falls into two counties and has been associated with two larger district. The upper stretch, in the Hellgate district in Broadwater County, was known for its placer deposits, while the lower portion, in the Missouri River district in Lewis and Clark County, contained both lode and placer mines (See Missouri River - 101). Prospectors worked the placer gravels along Magpie Creek with drift mining during the late 1890's (Sahinen 1935; Lyden 1948).

Belt series rocks underlie the Magpie Gulch area. A major quartz diorite dike, cutting through these rocks near the headwaters of the creek, provides at least one source for the placer gold found in the upper stretches of the gulch (Sahinen 1935).

Interest in the Magpie placers resumed during the 1930's. The sub-district gravels yielded $1,467 in 1931, and a single patented claim, the Sheriff, produced 75.3 fine ounces of gold in 1934. Placering continued as late as 1939, although there is no record of production for that year (Lyden 1948).


Although not described in the literature, the Hellgate district appears to take in the upper reaches of the drainage near the head of Hellgate Gulch, as well as the middle part of the canyon where the Argo mine is located. The Avalanche Creek subdistrict encompasses the upper portion of the creek, particularly the area around the mouth of Thompson Gulch. The Magpie Gulch subdistrict includes the length of the drainage as well as the tributary Bar Gulch.

Figure 1 shows the Hellgate district as described by the AMRB (1994) with smaller areas defined to show the Avalanche Creek and Magpie Gulch sub-districts. The latter areas were described by Lyden (1948).


Argo Mine

The Argo mine is located on the east side of Hellgate Gulch, about 7.5 miles above the mouth of the creek. Mike Finch discovered the mine prior to 1900, and development work was well under way by 1901, with Messrs. Matin and Canoll driving tunnels to reach the ore body. A year later the Eclipse-Argo Company reported the mine's first production, and by 1903 the new mill was turning out ten tons of concentrates daily. Employment reached 30 men by 1906, increasing to 65 by the time the mine operations shut down in 1910. Castleton Copper Company took over operations from 1916-1917, followed by the Furnace Creek Oxide Copper Company through 1918. The price of copper dropped that year, and the mine was idle by 1919 and reported production only one more time, in 1923. Although there was sporadic work over the next few years, both the mine and mill were closed by 1928 (Pardee and Schrader 1933; Western Mining World, 7 September 1901, 21 February 1903; Mining World, 22 August 1903; Walsh 1906; Walsh 1910).

Argo mine operators milled low grade ore in a 40-ton concentrator at the mine site and shipped both the concentrates and high grade ore to the East Helena and Washoe smelters. In 1910 the mill included a crusher, two sets of rolls, three Hartz jigs, and two Wilfley tables. The concentrator was evidently enlarged to a 50-ton capacity during World War I (Ferguson 1908; Walsh 1910; Hall 1910; Pardee and Schrader 1933; Reed 1951).

Reported ore values varied. Argo mine operators noted one especially rich batch of ore that averaged 35 percent copper. Pardee and Schrader (1933) place the average ore value from 1902-1918 at 25.6 percent to 27.57 percent, while Reed (1951) reported the average recovered metal content at just 6.5 percent copper. The mine produced a total of 2,997,787 pounds of copper with a net value of over $500,000 (Mining World, 22 August 1903; Pardee and Schrader 1933; Reed 1951).

Other Mines and Claims

There are several claims of lesser importance in the Hellgate district and associated subdistricts. The Conshohocken mine takes in several claims across the gulch and just upstream from the Argo mine. The Rex claim is found in Gabisch Gulch, a tributary of Hellgate Gulch. The Lee Mountain claim, worked by the Ideal Mining Co., is located on Lee Mountain, three miles above the Argo Mine on the east side of Hellgate Gulch. A. J. White, Jr., located another claim higher on the ridge above the Lee Mountain mine. Across Hellgate Gulch, White and others worked the Finchville and Winnie claims. In Magpie Gulch, O. L. Whitmire developed several claims about two miles upstream from the mouth; 16 tons of ore from the mine yielded 17 percent copper at the smelter. Finally, J. E. Walston dug several prospect pits on his claims in Bar Gulch, a tributary of Magpie Gulch. Aside from the Whitmire claims, there are no records of production for any of these mines (Pardee and Schrader 1933).


Ferguson, J. A.

1908 Eleventh Biennial Report of the Bureau of Agriculture, Labor, and Industry of the State of Montana for the Year Ending November 30, 1908.

Greiser, Sally T., Heidi A. Plochman, T. Weber Greiser, Daniel F. Gallacher, Robert J. Ottersberg, and Donald L. Smith.

1983 Class III Cultural and Paleontological Resource Inventory at Canyon Ferry Reservoir, Near Helena, Montana. Prepared for the U.S. Department of the Interior, Bureau of Reclamation, Billings, Montana, by Historical Research Associates, Missoula.

Hall, J. H.

1910 Twelfth Report of the Bureau of Agriculture, Labor and Industry of the State of Montana for the Year 1909 and 1910.

Lyden, Charles J.

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Mining World

1903 22 August.

Pardee, J. T., and F. C. Schrader

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Reed, Glenn C.

1951 Mines and Mineral Deposits (Except Fuels) Broadwater County, Mont. Information Circular 7592. United States Department of the Interior, Bureau of Mines.

Sahinen, Uuno Mathias

1935 Mining Districts of Montana. Unpublished Master's thesis, Department of Geology, Montana School of Mines, Butte.

Walsh, William

1906 Biennial Report of the Inspector of Mines of the State of Montana for the Years 1905-06.

Walsh, William

1910 Biennial Report of the Inspector of Mines of the State of Montana for the Years 1909-10.

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1901 7 September.

1903 21 February.