See also Elmore County Idaho Gold Production
Bear Creek and Red Warrior Districts
Commodities: gold, silver
Deposits in the vicinity of Rooky Bar, 65 miles by road from the Union Pacific Railroad at Mountain Home, around which these two districts center, were discovered about 1862, but were little developed until almost 10 years later. It has been estimated that the lode mines of the Bear Creek district produced about $2,000,000 in gold and silver and about an equal amount in gold from placers up to 1882.
Operations continued into the nineties, but data as to the amount produced are not available. The lodes of the Red Warrior district are thought to have produced less than those of the Bear Creek district, but the placer production is locally reported to have been large. Revivals of interest have yielded little production in either district.
The area is underlain by the Idaho batholith, in places cut by related dikes and others of later age. Most of the veins strike nearly east and consist of quartz lenses along shear zones which contain auriferous pyrite and minor amounts of galena and sphalerite. Transverse faulting is said to introduce local complications. The lode system is reported to have been traced some distance beyond the area known to contain ore shoots.
Blackstone District
Possibly the same as the Volcano district, p. 50 of this pamphlet. One property here listed in 1932 report of the State Inspector of Mines.
Black Warrior District
Commodity: gold
This district is about 15 miles northwest of Atlanta and is connected with it by a road now impassable to vehicles. A little development on several veins in the Idaho batholith and a small amount of placer mining have been done here. The lodes are presumably like those of the Yuba and other districts in the vicinity.
Dixie District
Commodity: gold
In the early days, this district, which is 30 miles from the Union Pacific Railroad at Mountain Home, produced some gold from lodes presumably like those of the Neal district and others along the southern border of the Idaho batholith, but has had little activity recently. It is not to be confused with the district of the same name in Idaho County.
Featherville District
Commodity: gold
This is a placer district, 56 miles by road from Mountain Home on the Union Pacific Railroad, and one of the areas in which dredging has been extensively practiced. In 1922 to 1927, when most of the dredging was done, Mineral Resources credits Elmore County with the production of 32,777 ounces of placer gold mainly from this dredge.
Neal District
Commodity: gold
This district, near the Arrowrock Dam and about 25 miles from Boise, was discovered in 1889 and produced about $2,000,000 in lode gold through 1895. Subsequent production has been small and, except for prospecting in the last few years, the district has long been almost inactive.
The district is within the Idaho batholith. Porphyritic and lamprophyre dikes are present, and the latter are associated with the lodes which are quartz lenses with pyrite, gold, galena, sphalerite, arsenopyrite, and locally garnet in seriticized and carbonatized granitic rock. There are small transverse faults.
Pine Grove District
Commodities: gold, silver
This district, 43 miles by road from the Union Pacific Railroad at Mountain Home, contains a number of lode prospects and a few small placers. The principal development has been at the Franklin Mountain mine, which is reported to have produced slightly over $750,000 in gold and silver, This mine shut down in 1917 and only a little prospecting has since been done there in search of faulted or otherwise interrupted ore shoots.
The district is within the Idaho batholith. Near the Franklin Mountain mine there are numerous stringers and dikes of pegmatite that locally at least are pre- ore. Ballard reports that there are dikes of diorite, rhyolite, and diabase which are out by the lodes, but the evidence for this is not clear as the workings appear to have been inaccessible since long before Ballard's visit and no dikes other than pegmatite were noted by the present writer during an examination of the surface near the mine in 1929.
The veins follow shear zones in sericitized and somewhat silicified granitic rock. The vein quartz contains pyrite, galena, sphalerite, and locally arsenopyrite and chalcopyrite. It is reported that most of the development in the Franklin Mountain mine was on two veins that strike about N. 20° W., dip steeply east, and belong to a series distributed through a zone about 1-1/4 miles wide. Cinnabar is reported to have been formed in stringers in the granitic rook, but these have not been productive,
Roaring River District
Commodity: molybdenum
This district, reached by trails about 15 miles long from Featherville and Rooky Bar, is noted mainly for its molybdenite prospects. It is underlain by the Idaho batholith cut by dikes of aplite, diorite, and lamprophyre. Molybdenite is in places disseminated in the granitic rook, but most of it is associated with quartz veins, in part brecciated and locally containing feldspar and other pegmatic material. Other minerals in the deposits include pyrite, specularite, chalcopyrite, marmatite, fluorite, and calcite. The lodes, especially in the more pyritic portions, are reported to contain gold and silver.
Snake River Placers
Commodity: gold
Placers along Snake River have been worked at King Hill and Glenns Ferry.
Volcano District
Commodities: silver, copper
This is a little known and little developed district in the southern part of the Idaho batholith, close to Hill City, the terminus of a branch of the Union Pacific Railroad. Dikes of aplite and of several kinds of porphyry are reported to cut the granitic rook and basalt and rhyolite flows locally cover it. There are several quartz veins stained with copper, manganese, and iron, and locally containing chalcopyrite, pyrite, galena, and sphalerite. A little mining has been done from time to time, some since 1930, and a little silver ore has been found. Some of the dikes, which are locally mineralized, may be Tertiary so the lodes may have a resemblance to the Tertiary lodes of the Boise Basin.
Yuba District
Commodities: gold, silver
This district, 80 miles by road from the Union Pacific Railroad at Mountain Home, is also termed by some the Atlanta or Middle Boise district, and the area along its southern margin is sometimes called the Hardscrabble district. The area was discovered in 1864 and active mining continued at least into the eighties with intermittent activity since then. In 1929, the Boise-Rochester, one of the principal mines, was reopened. It soon became one of the most active gold producers in the state, but was again shut down in 1936. It has produced ore valued at not less than $6,000,000, of which at least $2,500,000 were produced in 1931 to 1936.
The district is underlain by the Idaho batholith, which here varies somewhat in composition. There are aplitic and other dikes related to the batholith and some later porphyries also. The aplitic dikes are altered, especially near the lodes, but the porphyry dikes are fresher and not known in the mineralized areas.
Apparently there is one nearly continuous vein known as the Atlanta lode, with probable breaks and branches, and along which the principal mines of the district extend for 2 miles with a trend of about N. 20° E. There are also a number of subsidiary lodes of northwest trend that are supposed to branch off the main lode. In addition, especially in the outlying parts of the district, there are veins apparently not connected with this lode system, which as yet have produced little.
The Atlanta vein and its main branches correspond in trend to the principal sets of joints in the granitic rock. It is thought that circulation of mineralizing solutions along the joints softened the neighboring rock while concomitant and subsequent earth movements were concentrated along these zones of increased weakness, producing the shearing now so conspicuous.
The wall rocks, especially at some distance from the lodes, were sericitized. In and near the lodes, the rook was silicified and quartz veins deposited. The relatively rich ore formerly mined contained stephanite, pyrargyrite, and other silver minerals, but these are exceptional in the ore mined recently, in most of which pyrite is the only sulphide visible. The mill heads during the recent boom averaged slightly less than half an ounce of gold and from 1 to 2 ounces in silver to the ton.
