See also Shoshone County Idaho Gold Production
Black Prince District
Commodity: copper
This district (also known as the East Coeur d’Alene) is served by the Chicago, Milwaukee and St. Paul Railroad along the St. Joe River. It is underlain by the Belt series intruded by monzonite and by aplite and diabase dikes. Several prospects exist, but, so far as known, none has received much development. They show quartz veins with some chalcopyrite in contact metamorphosed rocks.
Coeur d’Alene Region
Commodities: lead, silver, zinc, gold, tungsten
This rather small area (roughly 500 square miles) in the upper drainage basin of the Coeur d’Alene River contains eight mining districts and has the longest sustained and by far the largest production of any part of the state. It is served by the Northern Pacific and Union Pacific railroads and by good highways.
The region includes the Coeur d’Alene or Shoshone district (a relatively little developed area north of Murray), the Eagle district that contains the gold placer and lode mines at which activity, in the region began, the Evolution district in the southern part of the region which has only recently come into preeminence because of the large silver production of the Shoshone mine; the Hunter or Mullan district with its famous old copper mines in the southeast part of the region; the Lelande or Burke district, immediately north of the Hunter, which contains some of the best known lead-silver mines of the region, such as the Hecla, Hercules, and others; the Placer Center or Wallace district in the south-central part of the region (containing such famous mines as the Tamarack and Interstate-Callahan with complex lead-zinc ore); the Summit district, southeast of but not clearly separated from the Eagle (a relatively unproductive area); and the Yreka or Kellogg-Wardner district in the southwestern part of the region which includes the Bunker Hill and Sullivan mine, the most productive in the region, as well as several other properties. The part of the Yreka district that is drained by Pine Creek contains lodes with relatively abundant zinc and is sometimes designated the Pine Creek district.
Prospecting began in the region in 1878, and active development of the gold placers and lodes near Murray in 1884 and continued for 10 years, with a recent short revival due to dredging. The beginning of development of the lead-silver lodes soon followed and by 1889 was in full swing. Copper came into prominence with the opening of the Snowstorm mine in 1904, attained maximum production in 1908, and has gradually declined since. Production of zinc began in 1905, and, with some fluctuations, has increased since. Tungsten and antimony have been produced, especially during the World War, but neither has attained much importance.
In recent years, the number of producers in the region has ranged from 30 to over 60. From 1884 to 1931 the aggregate production (according to Mineral Resources) has been $7,180,151 in gold; 262,277,378 fine ounces of silver; 82,676,978 pounds of copper; 4,406,687 short tons of lead; 853,130,752 pounds of zinc (spelter), and the total value is $731,374,415. Except for the temporary marked increase during the World War and decrease in the early thirties caused by the widespread business depression, the production of the region has from the beginning mounted at a fairly steady rate. There seems no reason to doubt that it will continue, in general, to do so for some time to come.
Most of the region is underlain by slate, quartzite, calcareous shale and strata of intermediate composition, all belonging to the Belt series and aggregating many thousand feet in thickness. The Burke and Revett formations, which include the purest quartzites in the region, contain the principal productive lodes, but mineral deposits are known in most of the different kinds of rock in the region. A number of the valuable ore bodies are in the upper part of the quartzitic slate of the Prichard.
Masses of monzonite and syenite crop out at intervals in a northeasterly direction across the central part of the region and there are also dikes of diabase and lamprophyre, some of which follow major faults. No large ore shoots are known in the granitic rocks, but sulphide minerals are present in such rock in several places. Locally, the lamprophyre is later than the mineral deposits, showing that ore deposition and igneous intrusion are closely related in age.
The strata are folded and are broken by numerous large faults, both normal and reverse. The Osborne fault along the valley of the South Fork of Coeur d’Alene River, with a supposed horizontal component of about 12 miles is an outstanding feature of the structure. The mineralization tends to be most pronounced in the areas of greatest structural complexity, but the lodes follow minor fractures rather than major faults.
Most of the ore deposits, including nearly all with large production, are roughly tabular masses formed dominantly by replacement and only to a relatively minor extent by fissure filling in shear zones, commonly in quartzite and locally in argillaceous and other rocks. In many the ore shoots are continuous for long distances, both horizontally and down the dip; in others there is a succession of closely spaced, irregular, ore shoots. They contain galena, sphalerite, siderite, and quartz in varying proportions; in some lodes the galena and siderite, in ethers the sphalerite and quartz, being dominant. Pyrite is commonly and pyrrhotite and chalcopyrite locally present in minor amount and barite is conspicuous in a few lodes.
Numerous other minerals are known in small amounts. Zinc is relatively abundant in the lodes in the vicinity of Pine Creek and in the corresponding position on the north side of the Osborne fault north and northeast of Wallace. It also tends to increase with depth in some mines. There is reason to think that sphalerite and much of the quartz were deposited early and have been in part replaced by the somewhat later siderite and galena that form the outstanding constituents of most of the ore so far mined. Much of the ore is fine-grained, and the galena commonly shows the results of crushin
Some of the lead-silver lodes of the type above described contain sufficient copper in chalcopyrite and tetrahedrite to be a valuable by-product. In addition, there are certain sideritic veins, largely in the southern part of the region,that are mined mainly for their chalcopyrite content. These also contain considerable pyrite magnetite and locally barite, but relatively little galena or sphalerite. Fissure filling was a greater factor in these cupriferous lodes than in those rich in lead. Several commercially productive copper ore bodies have been developed, but a number of the prospects on deposits of this sort appear from available descriptions not to be very promising.
Contact metamorphic phenomena are locally conspicuous in the quartzitic and argillaceous rocks near monzonitic masses, but in only a few places, such as the Success, Rex, and Helena-Frisco lead-zinc mines, have sulphides been deposited in connection with such phenomena in sufficient amount to have yielded much ore.
The Snowstorm, near Mullan, is the only copper mine in the region that has been very productive. Development here began in 1903 and production ceased in 1915. This deposit is a zone of dissemination of minute particles of bornite, chalcocite, chalcopyrite, and tetrahedrite, and their oxidation products through a certain stratum of Revett quartzite. Oxidized ore constituted a large part of that mined. It was stoped to the 600-foot level and locally persisted to the 1600-foot level.
The ore shipped in 1904 contained 4 per cent copper, 6 ounces of silver, 0,1 ounce of gold to the ton. That concentrated in 1912 contained 2,75 per cent copper. Mining ceased after unsuccessful attempts to find the ore body beyond a reverse fault against which it terminated. Other similar lodes are known in the vicinity, but are mostly of lower grade and so far none has attained comparable production.
The principal gold lodes, now largely exhausted, are near Murray, They are fissure veins with quartz, pyrite, chalcopyrite, galena, sphalerite, and free gold, the sulphides being in relatively small amount. Certain of the veins of this sort contain enough scheelite to constitute tungsten ore under favorable market conditions such as existed during the World War. This area also contains placer deposits, the richest of which has already been mined.
For a long time most of the ore mined in the region has been essentially free from the effects of oxidation and in many of the lead lodes sulphide was plentiful at or close to the surface. On the other hand, a few lodes show abundant oxidation to depths of well over 900 feet. Secondary enrichment does not appear to be of much commercial importance in this region. Even in the Snowstorm copper mine most of the chalcocite is regarded as primary.
St. Joe District
Commodities: copper, gold
This ill-defined district embraces the upper drainage basin of the St. Joe River. The prospects are reached by trail from Avery on the Chicago, Milwaukee and St. Paul Railroad. Those near the state boundary are most readily accessible from towns in Montana. Numerous copper lodes have been prospected on a small scale and a little placer mining has been done.
The area is underlain by metamorphosed Belt strata, folded, much faulted, and cut by the large Wishards diabase sill (probably pre-Cambrian) and by related small sills and dikes. The Idaho batholith and its outliers crop out to the south and west. Most of the lodes are veins and disseminations containing pyrite, chalcopyrite, and siderite.
Many are in or near the Wishards sill. So far as present data go, the deposits appear to be of low-grade. The Ward mine, on the state boundary, is one of the few productive properties in the district and much of its production is credited to the workings on the Montana side of the boundary. It is a shear zone with numerous veinlets of quartz, calcite, siderite, with small amounts of chalcopyrite, pyrite, and chalcocite in the veinlets and disseminated through the sheared rock.
St. Regis District
Commodities: copper, gold
This district centers around Adair on the Chicago, Milwaukee and St. Paul Railroad. The principal mines are the Monitor, Richmond, and others between the state boundary and the loop in the railroad east of Adair. Production is small.
The district is underlain by Belt strata, cut by the Wishards diabase sill along the state boundary. The lodes are veins and disseminations in shear zones containing quartz, siderite, calcite, chalcopyrite, pyrite, and, in the upper levels, the oxidation products of the sulphides. The ore locally contains 0,2 to 0,5 ounce of gold to the ton.
Slate Creek District
Commodities: copper, lead
This ill-defined district lies north and northwest of Avery on the Chicago, Milwaukee and St. Paul Railroad, but most of its prospects are accessible only by trail, either from Avery or from Wallace.
The lodes are groups of veinlets and disseminations in shear zones in the Belt strata, containing quartz, siderite, and calcite and small amounts of chalcopyrite, pyrite, galena, sphalerite, and specularite.
Sliderock Mountain District
Commodity: copper
This area is south of the Chicago, Milwaukee and St. Paul Railroad and its prospects are reached by trails. Production so far is negligible.
The country rock is Belt strata, injection gneiss, and, in the south, monzonite. Most of the lodes are small quartz veins and ill-defined groups of quartz veinlets containing a little chalcopyrite and locally small amounts of gold, silver and lead. In the southern part of the area, there are conspicuous outcrops of vein quartz, as much as 20 feet wide, with locally a little pyrite. Apparently these outcrops belong to lenticular veins, which, on the surface, can not be traced far.
