By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Granite County, in west-central Montana, through 1959 produced a total of 710,000 ounces of gold - 376,000 ounces from silver lodes and 334,000 ounces from placers. The most prosperous period was 1881-93 when the Granite Mountain, Hope, and a few other silver mines were at their peaks. Most of the lode gold has been a byproduct of silver ores in the Flint Creek, First Chance, and Boulder Creek districts (Emmons and Calkins, 1913, p. 192).
Placers along Bear Creek in the First Chance district and along Henderson Creek in the Henderson district were also productive, mostly before 1900. Lodes and, to a lesser extent, placers continued to yield substantial amounts of gold until 1946, but their output diminished through the 1950's.
BOULDER CREEK DISTRICT
The Boulder Creek district is in the east-central part of Granite County, about 7 to 9 miles northeast of Philipsburg. Most of the gold has come from lode deposits that also yielded some silver, lead, and copper. There were intermittent placer operations along Boulder Creek and its tributaries through 1942, but production from these was small (Lyden, 1948, p. 40-41).
Although lode deposits were found in districts surrounding the Boulder Creek basin in the 1860's, important discoveries were not made on Boulder Creek and its tributaries until 1885 (Emmons and Calkins, 1913, p. 192). The district was active until 1906 when the Royal mine, the most productive in the district, was put under lease (Emmons and Calkins, 1913, p. 246-247) and thereafter activity declined. Production again increased during the 1930's after the price of gold was raised, but from 1943 through 1959, activity was minor.
The early lode production is not known. The Royal mine is credited with a production, principally in the late 1890's, of about $1 million (48,379 ounces) in gold, and a small production came from other mines (Emmons and Calkins, 1913, p. 246). Total gold production of the district through 1959 was about 58,450 ounces, including about 1,400 ounces from placers.
The country rock in the Boulder Creek district consists of extensively faulted and tilted sedimentary rocks ranging in age from Precambrian to Mesozoic and biotite granite of Tertiary age which intruded the sedimentary rocks. Some of the faults cut the granite. The ore deposits are chiefly fissure veins in the granite, in siliceous Precambrian rocks, and in Carboniferous or Mesozoic quartzite and impure limestone. A few replacement veins are in relatively pure Paleozoic limestone.
The most productive deposits are gold veins that contain small amounts of silver. A few veins are silver or silver-lead veins that contain a little gold. The principal sulfides of the gold ores are pyrite and galena in quartz gangue; the silver ores carry also tetrahedrite and sphalerite (Emmons and Calkins, 1913, p. 246-250).
FIRST CHANCE DISTRICT
The First Chance (Garnet) district is in northern Granite County in the drainage basin of Bear Creek, a tributary of the Clark Fork River. Both placer and lode deposits were found in the district. The placer deposits along Bear Creek and its subsidiary gulches were the most productive in Granite County and were among the more productive of the early placer, operations in Montana. The placer deposits were discovered in 1865, and up to 1917, according to Pardee (1918, p. 231-232), they produced gold valued between $5 million (241,900 ounces) and $7 million (338,660 ounces), mostly in the first few years of operation.
From 1917 through 1959 the district produced a minimum of 15,200 ounces, most of which was mined during the period 1939-42. The total placer production from the district through 1959 was between 260,000 and 355,000 ounces.
The lode deposits are valuable chiefly for gold, but some copper and silver have also been produced. The first lodes were located in the district in 1867 but were not exploited to any extent until 1896 (Pardee, 1918, p. 171-172). A continuous but fluctuating production was maintained through 1942. After World War II the district had only minor activity and was virtually idle through the 1950's. The total lode gold production through 1959 was probably 85,000 to 90,000 ounces. The total lode and placer production combined is probably between 345,000 and 445,000 ounces.
The rocks of the Garnet district are quartzite and shale of the Belt Series of Precambrian age overlain by limestone of Paleozoic age. These rocks were folded into a northwest-trending arch and were intruded by a mass of granodiorite of Late Cretaceous or Tertiary age. The ore deposits are in veins in the granodiorite and along bedding planes in quartzite and schist. Quartz is the dominant vein mineral; barite and ankerite are locally abundant.
The ore minerals are pyrite, tetrahedrite, chalcopyrite, galena, and in rare occurrences, gold tellurides and molybdenite. Most of the gold is associated with pyrite (Pardee, 1918, p. 172-177).
FLINT CREEK DISTRICT
Most of the mines of the Flint Creek (Philipsburg) district, which includes the Red Lion camp, are in a 3-square-mile area just east of Philipsburg. This district is the largest lode-gold producer in Granite County even though gold accounts for only 10 percent of the value of the ore. Silver forms the remaining 90 percent. Some lead, copper, and zinc have been produced but they are of no great economic importance.
From 1950 through 1959 the Algonquin mine produced large tonnages of manganese ore, which yielded gold as a byproduct. The principal mines of the district are the Granite, Bimetallic, and Hope mines.
Ore was discovered at the Hope mine in December 1864, and lodes were soon located in many other places in the district and in the adjacent region (Emmons and Calkins, 1913, p. 191-193). The town of Philipsburg, just south of the Hope mine, was founded in 1867.
The Granite Mountain mine, the most productive in the Flint Creek district, was located in 1872. From 1875 to 1892 it yielded about $20 million in silver and gold and for a time was the most productive silver mine in the United States (Emmons and Calkins, 1913, p. 202-203). The Bimetallic mine, on the same ore shoot as the Granite Mountain, began operations in about 1882. Because of the fall in the price of silver, the mine was shut down in 1893 and was consolidated with the Granite mine in 1898 under the name of the Granite-Bimetallic Consolidated Mining Co.
From 1898 to 1904 these mines produced silver ore valued at about $1 million a year, but in August 1905 they were again shut down because of the low price of silver and decreasing grade of the ore. In 1906 the mine was opened to leasers. With the exception of the depression years, 1930-32, the Flint Creek district maintained a substantial annual production through 1945, when activity slackened. From 1946 through 1956 only a small amount of gold was mined. No activity was reported from 1957 through 1959.
Early mining operations in the district were very expensive because of the remoteness of supply points. Milling costs were especially high; for example, salt, which was used in large quantities in silver mills, had to be transported from Utah and cost $120 a ton at Philipsburg in 1871. In 1883 the Northern Pacific Railway was completed through Drummond, only 30 miles from Philipsburg.
A railroad from Drummond to Philipsburg was completed in 1887 (Emmons and Calkins, 1913, p. 192), and low-cost shipment of ore to smelters at Helena, Anaconda, and Great Falls was made possible. Some ore, however, was still treated in silver mills near the mines.
The gold production of the Flint Creek district before 1904 was estimated by Emmons and Calkins (1913, p. 201, 203) to be worth about $3,200,000, or about 155,000 ounces. Total production through 1959 was about 260,000 ounces.
The rocks exposed in the mineralized area east of Philipsburg comprise the upper part of the Spokane Formation of Precambrian (Algonkian) age and sedimentary rocks of Paleozoic age. These rocks are intruded by granite and granite porphyry of Cretaceous or Tertiary age and are folded and cut by numerous faults of small displacement (Emmons and Calkins, 1913, p. 28-126; 201).
The precious-metal deposits consist of silver-bearing veins in granite and in sedimentary rocks and silver-bearing replacement deposits in calcareous sedimentary rocks (Emmons and Calkins, 1913, p. 201-219). The Granite-Bimetallic lode, which produced the bulk of the ore in the district, is in the granite. This lode consists of pyrite, arsenopyrite, stibnite, tetrahedrite, tennantite, galena, sphalerite, and small amounts of pyrargyrite, proustite, realgar, and orpiment in a gangue of quartz, rhodochrosite, and calcite. This ore contained 20 to 30 ounces of silver per ton and from $1.50 to $3.00 worth of gold per ton.
Much of the ore was enriched and secondary cracks are filled with pyrargyrite (ruby silver), argentite, and tetrahedrite (gray copper) and, locally, sphalerite and chalcopyrite. The secondary ore carried from 50 to 1,000 ounces of silver per ton and from $4.00 to $8.00 worth of gold per ton.
The replacement ore, which has been exploited chiefly in the Hope mine, consists of quartz, calcite, fluorite, barite, and rhodochrosite, and the ore minerals are argentite, chalcocite, and argentiferous tetrahedrite. Pyrite and galena are rare, because much of the ore was oxidized. There is almost no gold in this type of ore (Emmons and Calkins, 1913, p. 163).
Located along Henderson Creek about 10 to 12 miles north of Philipsburg, the Henderson placers were discovered in 1866 and yielded gold valued at about $300,000 prior to 1870. By 1913 the total placer gold production was estimated at more than $1 million (48,379 ounces) (Emmons and Calkins, 1913, p. 263).
The deposits were worked by sluicing and, where the gravel was coarse and contained large boulders, by drifting. In about 1936 scheelite-bearing sand was discovered in these placers (Hund-hausen, 1949, p. 2), and they were mined throughout World War II. The district was inactive from 1950 through 1959. Total gold production through 1959 was about 81,800 ounces, including about 1,300 ounces from lodes between 1932 and 1949.