See also Valley County Idaho Gold Production
Big Creek District
Commodities: gold, copper
This district is reached only by trails leading east from the end of the Forest highway near Edwardsburg. Its remoteness from present and past routes of travel has hampered development, but there are a number of scattered prospects and two, the Jensen and Iron Clad, have produced some gold.
The district is on the margin of the Idaho batholith and is largely underlain by the dioritic and gneissic rocks related thereto. There are also areas of relatively unmetamorphosed quartzite of the Belt series, of Casto volcanics (Permian?), and of Challis volcanics (Tertiary), as well as porphyritic dikes and small granitic masses of probable Miocene age.
At the Jensen, there are lenses of quartz with chalcopyrite, pyrite, and pyrrhotite, and pockets of coarse gold in a shear zone in gneissic biotite diorite.
The Iron Clad property includes a breccia zone in quartzite containing auriferous iron-stained quartz, and in another place a number of small quartz lenses in quartzite with disseminated chalcopyrite and pyrite.
See also Valley County Idaho Gold Production
Deadwood District
Commodities: lead, zinc, gold, silver
This district, comprising the drainage basin of Deadwood River, is served by a highway leading to Cascade, 52 miles to the northwest, on a branch of the Union Pacific Railroad. There has been intermittent work here since the nineties, the principal development being in 1924 to 1932 by the Bunker Hill and Sullivan M. S.& C. Company at the Hall-Interstate and Lost Pilgrim groups. This company milled considerable lead-zinc ore, but in 1932 ceased operations here. In addition there are several small mines on gold-quartz veins and in the past a little placer mining was done. A dam across Deadwood River for power purposes has been built.
The district is in the south-central part of the Idaho batholith. There are small dikes of lamprophyre, pegmatite, and felsitic porphyry, and here and there small schist inclusions. The lodes worked by the Bunker Hill and Sullivan are quartz lenses with a little siderite and irregularly distributed sulphides in and close to schist inclusions. The irregular character of the ore shoots and extensively crushed and kaolinized rook introduced difficulty in operation. In much of the ore, sphalerite is more abundant than galena, and pyrite is fairly plentiful.
Edwardsburg District
Commodities: gold, copper, lead
The Edwardsburg district, which includes in its northern part what is often termed the Ramey Ridge district in Idaho County, and in its southern part the area commonly called the profile district, is in the upper drainage basin of Big Creek. It is at the end of a road, 94 miles long, through Warren to a branch of the Union Pacific Railroad at McCall, open only in the Sumer.
A few of the mines are reached by branch roads, but most are accessible only by trail. A recently completed road from Yellow Pine into this district passes over lower divides and, therefore, much improves transportation conditions. This road passes through Profile Gap in the center of the Profile district. Deposits have long been known here, but most of the activity dates from about 1903. Since then, a number of prospects and small mines have been opened, but the total production has been small.
The district is mainly underlain by quartzitic Belt strata with intercalated, highly metamorphosed limestone, intruded by the Idaho batholith and by Tertiary porphyritic dikes. In the part known as the Profile district, a block of Paleozoic limestone and quartzite is included in the Idaho batholith. Volcanic strata correlated with the Casto volcanics (Permian ?) occupy part of the Ramey Ridge area, but are not known to contain lodes. Farther south and east there is a cap of Chall: volcanics. Alluvial deposits border the principal streams.
Most of the ore deposits are low-grade, gold lodes in zones of shearing and fracture scores to hundreds of feet wide and persistent for long distances on the strike. They are composed of breccia, sericitized, and silicified country rock interspersed with numerous, relatively small quartz veins along joints and in shear zones, Both the altered rock and the vein quartz are auriferous, much of the gold being associated with the sparsely disseminated pyrite. The scanty available information indicates that the ore is only partially free-milling and ranges in tenor a trace up to about a quarter of an ounce of gold to the ton, with occasional pockets of higher grade material.
Fluorite, tetrahedrite, stibnite, galena, sphalerite, molybdenite, and chalcopyrite are present in places. Some of the lodes contain enough of one or more of these minerals to be of economic interest. In most places oxidation is far from complete, even near the surface. The Paleozoic strata contain little developed copper and lead deposits of contact metamorphic type.
On Ramey Ridge, most of the lodes are lenticular bodies of quartz, containing pyrite and chalcopyrite, locally with siderite, in sheared and altered dioritic rock. They are much smaller and apparently less persistent than the lodes mentioned above, but some contain shoots which probably average an ounce or more of gold to the ton. Under present conditions, the principal interest is in the gold and silver, but copper has been found wherever development has progressed to the shallow depth necessary to encounter sulphides. Veins in the Belt strata near the southern end of the ridge are associated with contact metamorphic silicates and locally contain copper ore of good grade.
Gold placers have been worked on a small scale in several places and interest in them has recently been revived. It is reported that much of the gravel is of good grade, but that the abundant boulders are troublesome.
Hurdy Creek District
Commodity: gold
The 1932 report of the State Inspector of Mines lists two properties in this district which is near Carburton and contains gold mines. The location of the district is not sufficiently well known to be plotted on Plate 1.
Lake City District
Commodity: gold
The 1932 report of the State Inspector of Mines lists two properties in this area, which apparently is a placer district near McCall. It is not shown on Plate 1.
Thunder Mountain District
Commodity: gold
This area is about 15 miles by an old road impassable to automobiles from the end of the recently constructed road in the Yellow Pine district and the distance by the new road to the railroad at Cascade is about 80 miles. The inaccessibility of the Thunder Mountain district has long been one of its outstanding disadvantages, but the new road has greatly decreased this.
The district was discovered in 1895 and most actively developed in 1901 to 1907, in the early part of which period many people rushed there under the mistaken impression that the gold lodes were rich, whereas with minor exceptions they are large deposits of low tenor. The total production is probably a little less than $400,000, largely from the Dewey and Sunnyside, and mostly prior to 1909, when a landslide which destroyed the town of Roosevelt completed the discouragement of most who had lingered after the Dewey shut down in 1907.
The district is underlain by the Challis volcanics and the lodes result from local concentration under favorable structural conditions of tenuous solutions which appear to have suffused the light-colored rhyolitic tuff and flows in the upper part of the Challis volcanics over a wide area. The principal hypogene minerals are native gold, pyrite, quartz, and clay minerals. Much of the better ore averages 0.4 of an ounce of gold to the ton or less, and there are large mineralized areas of much lower tenor.
Some, at least, of the high-grade stringers that have occasionally been found are of supergene origin. Although placer methods were successfully applied to mining weathered material in the outcrops of the lodes, particularly the Dewey, prospecting for placer deposits in the streams of the district has as yet yielded little.
Warm Lake District
Commodity: gold
This little-developed area, nearly 40 miles by highway from the railroad at Cascade, contains prospects on auriferous quartz veins in the Idaho batholith. No description of it has been published.
Yellow Pine District
Commodities: gold, antimony, quicksilver
The settlement of Yellow Pine is about 65 miles by highway from the railroad at Cascade,and the Yellow Pine Company's camp is reached by a recently constructed road about 15 miles farther up the South Fork of the Salmon. Some of the deposits were known as early as 1875, but little was done prior to 1900 and the only extensive development, that of the Yellow Pine Company at Meadow Creek, began in 1928. This company started milling gold-antimony ore in 1932. Previous to this, only a few small shipments of antimony and gold ore, and a few flasks of quicksilver had been derived from the district.
The district is underlain by the Idaho batholith, here mainly granodiorite, with dikes of several kinds and numerous schistose inclusions. There is a large included block of calcareous and quartzitic strata, mainly Paleozoic. The Challis volcanis extend into the eastern part of the district.
Some of the antimony-gold lodes are individual quartz lenses a few feet in maximum width. High-grade streaks in these furnished most of the antimony ore formerly mined. Other lodes comprise quartz stringers and lenses in large shear zones, mainly in granodiorite. Dikes of pegmatite, aplite, and lamprophyre are commonly associated with the lodes. Post-mineral faulting is common, but the displacements are not large. Stibnite, pyrite, and locally a copper mineral, probably tetrahedrite, are disseminated both in the vein quartz and in the altered and silicified rook of the shear zones.
The Yellow Pine Company is mining ore of this character primarily for its content of precious metals (average perhaps a quarter of an ounce of gold to the ton). The antimony was regarded originally as a byproduct, but is likely to have greater relative importance in the near future. It has recently been found that scheelite is plentiful in some of the ore.
The quicksilver lodes are in a small part of the included block of sedimentary rock, mainly in more or less altered limestone which in and close to the ore is largely converted to jasperoid in which pyrite and cinnabar are disseminated, the latter in part filling cracks. The quartzite beds were impervious to the mineralization and in places bound it sharply. Elsewhere the ore is in irregular pipes in the limestone. In most places, in existing workings, the grade of the ore is low, but the amount of mineralized rock appears to be large.
