See also: Boise County Idaho Gold Production
Alpine District
The State Inspector of Mines' report for 1932 lists two properties in this district. No other data are available.
Banner District
Commodities: si1ver gold
This district is about 75 miles by highway from Boise through the Boise Basin and is included by some as part of the Gambrinus district. It is about 6 miles southeast of Lowman, but not readily accessible from there. In 1882 to 1894, it produced $1,500,000 to $2,000,000, but there has been little activity in the lode mines for many years. The deposits are large, well defined quartz veins in the rock of the Idaho batholith which carry pyrargyrite, argentite, and other sulphides with little or no gold. Placer mining has long been carried on here and the district is one of several in this part of Idaho in which dredging has recently been carried on.
Centerville District
Commodity: gold
This district, regarded by some as part of the Placerville district, contains some gold veins in granitic rock, but is principally known for its placer deposits, which were among the more productive deposits of the Boise Basin in the early days. In recent years, there has been dredging here, which was temporarily halted by the destruction of the dredge by a forest fire in 1931. The district is served by highways and by the Intermountain Railway, and is 44 miles from Boise.
Dry Buck District
No data available except that the 1932 report of the State Inspector of Mines lists a property there.
Cold Springs District
No data available except that the 1932 report of the State Inspector of Mines lists a property there.
Gambrinus District
Commodities: gold, silver, lead
Most of the early lode mining in the Boise Basin was in this district, which is sometimes called the Elkhorn district, (6 miles by road from Idaho City) but there has been little recent activity. Most of the veins follow shear zones of northwest trend which cut aplite and lamprophyre dikes in the granitic rock of the Idaho batholith. The veins are mined mainly for gold, but some contain leadsilver ore.
Horseshoe Bend Coal District
Commodity: coal
The Horseshoe Bend coal district, not to be confused with the Horseshoe coal district in Teton County, has long been known and a number of prospects therein have been intermittently operated. Only a small amount of coal has been produced for local use. The district is about 20 miles from Boise and 40 miles from Weiser and is served by a highway and the McCall branch of the Union Pacific Railroad.
Along the valley of the Payette River near Horseshoe Bend, and in Jerusalem Valley a short distance up-stream, there is a mass of poorly consolidated sediments with associated basalt flows about 15 miles long, 1 to 4 miles wide, and about 1,000 feet thick. These strata rest in a depression on the surface of granitic rock belonging to the Idaho batholith. The sediments, which are slightly deformed by flexure and faulting, contain a few thin beds of sub-bituminous coal and lignite, that in most exposures are less than 14 inches thick.
Idaho City District
Commodity: gold
This district contains some of the most productive placers of Boise Basin as well as a number of small gold lode mines, but few of either have been operated extensively in recent years. It is served by a little-used railroad and by a highway from Boise, 36 miles to the southwest.
The placer workings were not only in the gravel of the present streams, but also in several older gravel deposits higher on the slopes. Some gold was found in local remnants of Miocene (?) sediments under the gravel, but these nowhere proved of much value. The lodes are probably similar to those of the Gambrinus district.
Moore Creek District
Commodity: gold
This district, a short distance south of Idaho City, contains placer deposits only and has not been as much developed as those farther north in Boise Basin. Some of the gold has come from the gravel of the present stream and some from gravel under Pliocene (?) basalt flows.
Payette River Placers District
Note: not on district map
Placer mining has been carried on intermittently along the Payette River, its south fork, and their tributaries, particularly in the vicinities of Banks, Garden Valley, and Lowman.
Pioneerville District
Commodities: gold, silver, lead
This district, about 50 miles from Boise, according to the usage which has been followed in the annual reports of the State Inspector of Mines, includes the areas termed by many the Summit Flat and Grimes Pass districts, which are shown separately on the district map.
It includes a number of base metal lodes, some valuable largely for silver, and, especially close to Pioneersville, placer deposits that were productive in the early days and have recently been reopened. In the early days, a few hundred thousand dollars came from lodes in the bedrock. All this was obtained by amalgamating the free gold in the shallow oxidized parts of the deposits. The sulphide ore has not yet been adequately tested although a little intermittent work has been done on it.
The country rock is the Idaho batholith cut by numerous Miocene (?) porphyry dikes. The principal mines are on shear zones in which pyrite, galena, sphalerite, and possibly other sulphides are somewhat irregularly distributed in a gangue of sericitized granitic rock with lenses of quartz and some calcite. In these lodes, the principal value is in the gold, although considerable amounts of lead and zinc exist and some recovery of these has been made. In some places, galena and other sulphides are irregularly and sparsely disseminated through somewhat altered and fractured granitic rock. Both of the above kinds of deposits are of probable mid-Tertiary age.
In addition, there are a few lodes of similar age, which, like those of the Banner district, contain ruby silver in addition to base metal sulphides. Recently one of these, the Comeback, has yielded some good silver ore.
Quartzburg District
Commodity: gold
The Quartzburg district includes the Gold Hill, Granite, and Placerville districts. The latter two, centering around the towns so-named are placer districts formerly much more productive than at present. The gold lode mines around and west of Quartzburg have probably produced well over $8,000,000. Several of them, such as the Gold Hill, Belshazzar, Mountain Chief, and Mayflower, are, or recently have been, active. The area is about 50 miles by highway from Boise and is also served by the little-used railroad terminating at Centerville, about 7 miles away.
The country rock is quartz monzonite of the Idaho' batholith, which is cut by numerous dikes, mainly porphyritic, of probable Miocene age. The dikes in general trend northeasterly and form part of the so-called "porphyry belt", which contains all of the principal lode mines of the Boise Basin. Most of the lodes are later than and genetically related to the dikes. The few, such as the Blue Rock, that appear to be related to the Idaho batholith are relatively undeveloped.
The Tertiary lodes include veins, mainly in the quartz monzonite, and stock- works, mainly in dikes, which comprise aggregates of small cracks subordinate to and at acute angles with the fractures and shear zones containing the veins. In most of the veins, ore shoots are individually small, but in places stoping has been carried over 1,000 feet down the dip. and as much as 3,000 feet horizontally.
Ore shoots tend to be localized at the intersection of veins and dikes, but are not confined to such places. The stockworks in the Pioneer workings of the Gold Hill mine, the only place where this variety of deposits has yet been mined, have locally been stoped continuously for as much as 100 feet in stope length, and are generally over 20 feet wide. Most of the ore in the stockworks is in thoroughly altered rhyolite porphyry, but it is by no means confined thereto.
Galenobismutite, tetradymite, arsenopyrite, pyrite, native gold, galena, and sphalerite are the principal hypogene (primary) metallic minerals in the Tertiary lodes of the district, although their proportions vary. Most of the sulphides are in quartz seams and veins although some, especially .pyrite, are disseminated in the wall rocks, which, in and near the lodes, are intensely sericitized and somewhat carbonitized. Much of the ore contains somewhat more than half an ounce of gold to the ton with occasional pockets of high-grade material.
Both here and in other districts in and near Boise Basin Tertiary lodes such as those described above have only recently begun to receive development at depth. Early mining was confined to the shallow oxidized parts of the lodes, but modern milling methods enable good recoveries to be made in the sulphide ore, most of the gold therein being free and apparently hypogene (primary).
As yet, little has been done with the bismuth and other metals in the ore, but these constitute possible by-products. The lodes, especially the stockworks are inconspicuous in outcrop and it is quite possible that well directed prospecting within the "porphyry belt" would result in new discoveries.
Twin Springs District
Commodity: gold
The Twin Springs or Highland district lies along the Boise River in the general vicinity of Arrowrock Dam, but its limits up and down stream are not accurately known. There has been intermittent placer activity here for a long time. The down-stream end of the district apparently also embraces some gold lodes similar to those in the Black Hornet and adjacent districts
West View District
Commodity: gold
This district and parts of it have received an unusual number of different names such as Gem, Payette River, Pearl, Rock Creek, Shaffer Creek, South View, and Willow Creek, The part of the district from Pearl west is in Gem County. Most of the lode mines are in Boise County, but much of the small amount of placer mining that has been done was in the western part of the district, especially along Willow Creek. The different parts of the area are within easy reach of railroad points and about 25 miles by highway from Boise, The production from 1870 to 1896 was estimated by Lindgren at about $80,000 in gold, and the amount mined since has been small.
Most of the district is underlain by granodiorite or a kindred rock. There are masses of augite diorite and dikes of several kinds, Lindgren regarded all of these as related to the Idaho batholith, but Kirkham believes that some masses are intrusive into the Payette formation. Patches of the latter and associated rhyolitic and basaltic necks and flows cover areas bordering the mineralized parts of the district.
Lindgren stated that the Payette and related volcanic rocks were later than the lodes and that the Payette included placers derived from the lodes. The suggestion is made that some of the rocks intrusive into the granodiorite may represent a continuation of the "porphyry belt” of the Boise Basin with which they accord in position and trend, and that therefore some of the lodes here may have affinities to those of the Quartzburg district.
Most of the lodes are veins in the granodiorite, but some are in augite diorite and in dioritic porphyry dikes. The ore is in narrow seams in shear zones in altered rock, and contains pyrite, arsenopyrite, sphalerite, galena, and rarely chalcopyrite and ruby silver, and some quartz and calcite. Much of that mined in the nineties contained as much as 5 ounces to the ton in gold.
