See also Lemhi County Idaho Gold Production
Aurora District
Commodity: gold
This name is sometimes applied to the part of the Mackinaw district opposite the settlement of North Fork, It contains formerly productive placer deposits.
Blackbird District
Commodities: copper, gold, cobalt, nickel, silver
The northern part of this area contains copper-gold and cobalt-nickel lodes, while the southern part, sometimes called the Musgrove district, contains selenium-bearing gold-silver ore. The district, which is about 35 miles from Salmon by a recently improved road, and is also conveniently approached from Challis, about 60 miles away, was discovered in 1893 and from then until about 1902 there was considerable activity at and near the Blackbird copper mine, During the World War, cobalt-nickel deposits, 3 or 4 miles southeast of this locality, were prospected and partly developed, but the results do not appear to have been encouraging as the property has long been deserted.
The precious metal deposits of Musgrove Creek have been known for many years, but were principally developed in 1913, 1914, 1915, and 1921. About $35,000 has been produced, mainly from the Musgrave mine.
The predominant rock throughout the district is more or less argillaceous. Quartzite of the Belt series cut by a few gabbro and lamprophyre dikes presumably related to the granitic stock of variable composition that crops out to the northeast, This stock is thought to be an outlier of the Idaho batholith, A remnant of the Challis volcanics extends into the southwestern part of the district and this formation probably covered much of the area before being removed by erosion. Rhyolite dikes probably related to the lava are exposed along musgrove Creek.
The copper-gold and cobalt-nickel deposits are interrelated and differ only in proportions of the minerals and in structural details. They are irregular and discontinuous veins and lenticular masses of quartz and mineralized quartzite commonly localized in schistose parts of the quartzite, the schistosity being apparently related to and concommitant with the mineralization which probably took place under high temperature and pressure.
The known hypogene metallic minetals are pyrite, chalcopyrite, nickeliferous pyrrhotite, galena, cobaltite, smaltite, arsenopyrite, and magnetite, and the gangue minerals include quartz, biotite, calcite, siderite, garnet, and tourmaline. The shallow, oxidized parts of the cupriferous lodes contain enough gold to have been prospected for this metal.
The precious metal deposits along Musgrove Creek have yielded ore containing $10 to $20, and locally as much as $70 to the ton of gold and silver, at least in part as selenide. They are essentially like those of the Parker Mountain and similar districts except that the enclosing rock is quartzite instead of lava or tuff.
Blue Wing District
Commodity: tungsten
Mineralization here has been known since 1881, but development of the tungsten deposits, which distinguish it, did not begin until 1911. Some tungsten ore was produced in 1911 to 1917 at the Patterson and Boise-Ima mines, and development was renewed in 1927 and 1929. Since 1934, there has been a marked increase in activity and the district has become one of the larger tungsten producers in the United States. The district is now generally approached from Mackay, the terminus of a branch of the Union Pacific Railroad, about 80 miles away.
The deposits are in fractures and shear zones, locally as much as 20 feet wide in argillitic quartzite of the Belt series close to the border of a buried granitic mass. Sharp bends and step-like offsets, not formed by post-mineral faulting, are characteristic. The ore consists of glistening white quartz interlayered with or containing fragments of partly replaced quartzite, with chlorite, pale yellow mica, molybdenite, hubnerite, pyrite, galena, argentiferous tetrahedrite, sphalerite, and chalcopyrite irregularly but rarely abundantly distributed through the quartz.
Districts east of Salmon
Commodity: gold
The Carmen Creek, Eldorado, Kirtley Creek, and Pratt Creek (including the Sandy Creek) districts are grouped along the west flank of the Beaverhead Range near Salmon. Short roads and trails connect them with the highway in Lemhi Valley. Together they may have produced roughly $1,000,000, in part from placers, in part from gold veins containing some base metals. Some of these districts, especially the Eldorado, are extended by some to include areas south of Lemhi Valley, but, as Plate 1 shows, this practice is not here adopted.
The country rock is mainly quartzite of the Belt series with locally dioritic dikes and larger granitic intrusions. Most of the lodes are quartz veins with pyrite, chalcopyrite, and lesser amounts of galena and sphalerite. Some are lenticular quartz masses in zones of intense schistosity into which mineralization has spread with the development of disseminated pyrite, chalcopyrite, magnetite, actinolite, and epidote. There has been some oxidation and copper sulphide enrichment.
Eureka District
Commodities: gold, copper
This district is near Salmon and is crossed by the highway along Salmon River. A number of the smaller properties are, however, only accessible by trail.
Cupriferous gold lodes were mined in the early days and since about 1917 copper lodes with little gold have been productive, with brief interruptions, on a small to moderate scale, up to recent years when the sharp decline in the price of copper compelled suspension of operations. A portion of the area northwest of Salmon, which contains lodes with relatively plentiful galena is sometimes called the Silverton district, after the principal prospect.
Much of the district is underlain by argillaceous quartzite of the Belt series, locally schistose. In the northern and western parts of the area a granitic stock presumably related to the Idaho batholith is exposed. The valleys of the Salmon and Lemhi rivers are bordered by Tertiary tuff, sandstone, and some lava, with a few lignite beds, some of which were mined for local use before the railroad made it possible to ship in better fuel.
The gold lodes are mainly small quartz lenses in the granitic stock near its contact with the quartzite and contain auriferous pyrite, chalcopyrite, and a little galena. The copper deposits are replacements in shear zones with subordinate quartz lenses. The hypogene minerals comprise quartz, micas, chlorite, epidote, chalcopyrite, pyrite, magnetite, specularite, delafossite, and locally sphalerite and barite, The ore averages 2-1/2 to 6 per cent, rarely as much as 20 per cent, copper with negligible amounts of precious metals. The ore near the surface is oxidized and some stopes are reported to contain abundant supergene chalcocite, but much of the material mined is free from the effects of surface processes.
Gibbonsville District
Commodity: gold
This district, sometimes called the Hughes Creek and Dahlenega, is traversed by a highway and is about 30 miles from Salmon on the Gilmore and Pittsburg Railroad,
The placers of this area were discovered in 1877, and gold lodes were actively worked from about 1880 to 1898, with intermittent development in both lodes and placers up to the present, total production is roughly $2,000,000, mostly from placers,
The area is underlain by quartzite and slate of the Belt series, intruded by gneissic quartz diorite, probably Mesozoic but thought by some to be possibly pre- Cambrian. A small remnant of Tertiary lava remains.
The lodes are narrow, steep. quartz veins with auriferous pyrite, locally massive, and in places calcite and chalcopyrite. The primary ore averages half an ounce to 2 ounces a ton, of which 40 per cent is reported to yield to amalgamation. The veins are broken by a complicated system of faults which interfere with mining.
Gravel Range District
Commodities: gold, silver, opal
This district, sometimes called the Singiser, was discovered in the early seventies. It is somewhat over 100 miles by road from Mackay, the terminus of a branch of the Union Pacific Railroad. A little placer mining was done at that time, but the principal development began in 1896 at the Monument lode mine. There was intermittent lode mining in the area until about 1914. Since then, little has been done except a little assessment work and placer mining. An estimate of less than $100,000 in gold and silver, as the total production of the district, has been made; apparently a very liberal figure.
The mineralized part of the area is underlain by the Tertiary Challis volcanics. The Casto voloanics (Permian ?) crop out in the northwest part and the Belt series along Panther Creek.
In the Monument or Singiser mine, the ore follows fractures trending N. 20 to 40 degrees and dipping 40 to 65 degrees N.W. It contains quartz, a clay mineral like halloysite, pyrite, adularia and a selenide-like naumannite. The Rabbitfoot, the only other extensively developed property, shows widely silicified and kaolinized white rhyolite with here and there minor fractures lined with flakes of gold with or without quartz. The altered rhyolite contains sparse pyrite and is reported to carry gold. Much of the ore mined at the Monument is reported to have contained $11 a ton whereas that at the Rabbitfoot was lower grade. High-grade ore is reported to have been found at the Monument in the early days.
A prospect on silicified breccia zones in Tertiary tuff near Meyers Cove contains barite and stibnite in sufficient abundance to constitute antimony ore, providing a sufficient quantity is present.
Opals have been mined on Panther Creek. They occur in quartzite and in a porphyry dike or detached mass of the Challis volcanics, in Challis volcanics, and in placers elsewhere in the district. Although some stones of good quality have been found, they are so brittle as to be difficult to work and hence very little has been done on the deposits for a number of years.
In addition to gold and opals, some placer gravels contain cassiterite (tin oxide) in crystals, and as botriodal masses, but the amount recovered has been too small to be of consequence.
Junction District
Commodities: lead, gold, silver, manganese
As mapped on Plate 1, this district includes areas regarded by some as separate districts known as Bight Mile and Little Eight Mile districts, after creeks that flow through them, and in addition the area close to the town of Junction on the former Gilmore and Pittsburgh Railroad. Little mining was done prior to 1904 when the Leadville mine, the principal producer, was located, and in recent years the district has not been active. The total production has been nearly $300,000 in lead and precious metals.
The part of the district in the Beaverhead Range is mainly underlain by Paleozoic strata, largely Carboniferous limestone, with small dioritic intrusions. The part in the Lemhi Range contains both Belt and Paleozoic be a with similar intrusions . The intervening Lemhi Valley is underlain mainly by fertiary tuffaceous sandstone and related beds, masked by later gravels. A large mass of similar Tertiary clastic beds, including some marl, occupies the pass through the Beaverhead Range in the eastern part of the district, utilized by the highway into Montana.
Most of the lodes are irregular replacements in limestone or less commonly slate, almost without introduced gangue minerals. The principal metallic minerals are argentiferous galena, pyrite, chalcopyrite, and sphalerite. Some manganese oxides are present. In the Leadville mine, which is in Carboniferous limestone, post-mineral faulting has brought recent alluvial deposits into contact with the lode.
McDevitt District
Commodity: copper
This district lies on either side of Lemhi Valley, which is traversed by a highway. The part of the district north of the valley is included by some in the Eldorado district. It is reported that copper deposits in the district were prospected by Mormons who attempted a settlement in the Lemhi Valley in 1854 to 1857. The Copper Queen, the principal producer, was located in 1883 and has operated intermittently since 1905. Umpleby, in 1910, estimated the total production at $100,000, largely in gold. Since then, a somewhat larger amount has been produced largely in copper from the Harmony.
The district is underlain by quartzite and schist of the Belt series with local remnants of Paleozoic beds. Tertiary clastic beds, interbedded with lava on the mountain slopes, underlie Lemhi Valley and extend up the spurs on either side.
The lodes are in quartzite and locally chlorite schist of the Belt series. They follow shear zones, locally with marked brecciation, and contain quartz, a little calcite, pyrite, chalcopyrite, locally bornite, and in places limited amounts of free gold and oxidation products. In most of the better copper ore, the amount of precious metals is negligible, Specimens of bornite with visible gold have been found.
Much of the ore mined ranged from 2 to 7 per cent copper, although some was of higher grade.
Mackinaw District
Commodity: gold
This district is sometimes called the Leesburg district and the northeast part of it, mainly valuable for placer, is called by some the Moose Creek or Aurora district. The Mackinaw district centers around the old town of Leesburg, about 20 miles by road from Salmon. Leesburg once had a population of 7,000 people. Placers were discovered in this vicinity in 1866. The principal activity was in the following 14 years, although placer mining has since continued intermittently.
There has been a revival of interest since 1928. The placers in the general vicinity of Leesburg may have a total production of somewhat over $5,000,000 and those in what is sometimes called the Aurora district may have produced another $1,000,000. The lode mines, mainly the Italian and Shoo Fly, have contributed about $250,000 in bullion.
Much of the district is underlain by granitic and gneissic rocks belonging to a stock believed to be related to the Idaho batholith. The Belt strata covering the central part of the stock still remain. On Moose and Napias creeks, there are patches of Tertiary lava and sediments, A few rhyolite dikes, presumably Miocene, are present.
There are five intergradational types of lodes: (1) Narrow quartz veins accompanied by stockworks in granitic rock, which contain pyrite, sphalerite, specularite, and a little galena, represented by the Italian gold mine; (2) replacements along fault planes with quartz and pyrite, and abundant, somewhat mineralized gouge, as at the Gold Dust mine; (3) irregular replacement bodies of pyritiferous quartz, along shear zones in schist which contain garnet, epidote, and magnetite, represented by the Mayflower group; (4) small lenses in schist and probably also in granitic rock, that are supposed to be the sources of much of the placer gold; (5) quartz veins in contact with biotite monzonite dikes, with comparatively abundant chalcopyrite and sphalerite, and some pyrite and galena.
The last variety cuts deposits of the first named at the Italian mine. It may be perhaps of Miocene age. Lead ore is reported at the Bull of the Woods mine, but little is known about it. Nearly all the lodes are valued for their moderate to low-gold content, base metals being negligible.
Umpleby regards the earlier and more extensive placers as probably of both Miocene and Pliocene age. Proof of such antiquity is lacking. Much of the placer gravel is clearly later than Pleistocene (presumably Wisconsin) till on which it rests.
Mineral Hill and Indian Creek Districts
Commodities: gold, silver, copper, lead
These districts are 30 to 40 miles by highway from Salmon, but a number of the properties in both are not now accessible to vehicles.
The Mineral Hill district, discovered in 1882, has produced about $800,000, and the adjoining Indian Creek district, located in 1895, has produced about $600,000. In both, gold and silver have been the principal metals recovered although base metals are locally abundant enough to be of economic interest. Placer mining has not been an important factor in these districts. Intermittent operation of the lode mines has continued, but none of the properties has been worked on a large scale for many years. Recently, the Ulysses has been reopened.
The area contains schist and quartzite of the Belt series cut by gneissic and granitic rocks with associated pegmatite and aplite, and later, post-mineral dikes of several kinds. The gneissic rocks were formerly supposed to be Archean, but D. M. Davidson and Anton Gray have shown in unpublished theses at the University of Minnesota that they are intrusive into the Belt rocks and both gneiss and granitic rock are probably related to the Idaho batholith.
Some of the lodes parallel bedding or schistosity in the sedimentary rocks, but many are controlled by joints in the igneous rocks. The lodes were formed in part by fissure filling, in part by replacement. They are from a few inches to 15 feet wide and rarely of great horizontal extent and contain quartz, pyrite, chalcopyrite, arsenopyrite, galena, sphalerite, and locally calcite, magnetite, and muscovite. The wall rocks are silicified and sericitized and contain some sulphides.
Nicholia District
Commodities: lead, silver
This district, about 25 miles by road from Gilmore, is sometimes loosely included in the Birch Creek district. (p. 34) It was discovered about 1881 and was actively productive through 1889 with intermittent attempts to resume operation since then. Estimates of total production range from $2,500,000 to $5,000,000, mostly from the Viola mine.
The rocks of the district comprise folded and faulted Paleozoic limestone, quartzite, and shale, with a small granitic mass reported a short distance north of the area.
The Viola contained three large replacement bodies in magnesian limestone connected by stringers. The ore was load carbonate intermixed with iron and manganese oxides and contained from 20 to 60 per cent lead and 4 to 16 ounces of silver to the ton. Near the margins of the load ore bodies, now reported to be exhausted, there are deposits of smithsonite ore from which shipments were made in 1925 and 1926. Other properties in the district, mostly unproductive, contain similar, but, so far as developed, smaller and lower grade deposits.
Parker Mountain District
Commodities: silver, gold
This district was discovered in 1904, and is about 85 miles by road from Mackay, the terminus of a branch of the Union Pacific Railroad. The district was intermittently productive through 1915. Recently renewed prospecting has resulted in mining small, high-grade pockets and some development is reported on the larger lodes. The total production probably does not much exceed $10,000 obtained from carrying $10 to $20 a ton in silver and gold.
The deposits are veins and breccia zones in the Challis volcanics with banded chalcedonio quartz, selenides, native gold and very small amounts of chalcopyrite and other sulphides. A little fluorite is present locally.
Spring Mountain District
Commodities: lead, silver, copper
This district is about 8 miles from Gilmore. Lodes were found here in the early eighties and several small mines have been developed, but the total production is not large.
The district is underlain mainly by Paleozoic strata cut by quartz diorite dikes. Most lodes are replacements in limestone, containing lead ore similar to those in the Texas district, but one (the Bruce estate) is a copper deposit of probable contact metamorphic origin.
Texas District
Commodities: lead, silver, copper, gold, zinc
This small district, which centers around Gilmore, was discovered in the eighties, but produced little prior to 1902. From then through 1929 the production totaled $11,520,852 mainly in lead and silver, but including some gold, copper, and zinc. Most of the production came from the Pittsburg-Idaho mine. Little was done for some time after 1929, but there has been a revival of activity recently, in part occasioned by discovery of a pocket of rich silver ore south of Gilmore.
The principal ore bodies are in fracture zones approximately parallel in strike, but opposite in dip to the stratification of the enclosing Devonian (?) dolomite. Some mineralization follows fissures at right angles to the main lodes. The hypogene ore consists largely of quartz and simple sulphides formed by a combination of replacement and filling, but much of that so far mined is more or less thoroughly oxidized.
Wilson Creek District
Commodities: gold, silver
There are a few prospects for gold and silver ore in this little known district near the Middle Fork of the Salmon and farther down that river, particularly on the west side near its mouth, there are other gold prospects, both lode and placer, which do not appear to have been included in any named district. All these prospect are far from roads and the trails to some are scarcely passable by horses.
Yellowjacket District
Commodities: gold, copper, lead
Until recently this district was commonly approached from Mackay, the terminus of a branch of the Union Pacific Railroad, about 125 miles away. The road to Salmon, only about 50 miles long, has recently been improved.
Prospecting began here in the sixties and extensive development in the eighties, with most of the production in 1893 to 1897. There has been intermittent activity at both lode and placer mines since then. The records show shipment of $121,761 in bullion from the Yellowjacket lode mine, but the total from that property, the only one with any considerable production, has been estimated by Umpleby at $450,000, largely from ore averaging about 0.1 ounce of gold to the ton.
A number of other properties, both lode and placer, have produced gold and silver, but the aggregate amount is apparently not very large. Lead and copper ore is present and small shipments have been made. The placer production has been very small.
The district is underlain by argillaceous and locally calcareous Belt quartzites cut by dikes of altered diabase of probable pre-Cambrian age and by a variety of dikes and intrusive masses believed to bo of Tertiary age. The Belt strata are broken by large faults, one of which is an everthrust that may be of early date as it does not appear to affect the Casto volcanics (Permian ?) on the western border of the district.
The Yellowjacket lode is a shatter zone with numerous veins and stringers in more or less altered quartzite. Post-mineral faulting is present, but is apparently not of large displacement. Most of the production came from opencut workings on oxidized ore shoots containing altered pyrite and small amounts of lead and copper minerals in a gangue of quartz and ferruginous calcite. In underground workings, in part 400 feet below the open cut, sulphide ore containing massive galena with some chalcopyrite and pyrite in quartz is known, but as yet has been little developed.
In somewhat similar but smaller, and less oxidized deposits in the Columbia and other mines, chalcopyrite, tetrahedrite, and locally galena and sphalerite occur in quartz with some calcite in fractures and breccias in quartzite. The ore mined at the Columbia in the early days is reported to have contained an ounce and a half of gold per ton, locally more. The Copper Glance is distinguished by abundant chalcopyrite and supergene chalcocite and by siderite in place of calcite. Some copper ore has been shipped from this prospect.
At the Black Eagle, fractures in pre-Cambrian (?) diabase or gabbro are filled with quartz containing siderite, pyrite, specularite, chalcopyrite, and some calcite and sphalerite.
