Idaho History October 1, 2017

History of the Stibnite Mining District

Valley County, Idaho

Photo courtesy Valley County Sheriff’s office
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Excerpts from: “Midas Gold Stibnite Gold Project Valley County, Idaho Plan of Restoration and Operations” Appendix D

Stibnite Mining District History

The Stibnite Gold Project (Project) is located in the historical Stibnite Mining District (District) in central Idaho.

Over the past century, the District has been subject to considerable prospecting and exploration, underground and surface mining, milling, tailings disposal, smelting, ore heap leaching activities, spent ore disposal, waste rock disposal, hydro‐power development, water retention dam construction, forestry, saw mill, housing camps, the town of Stibnite with its multiple neighborhoods, and associated infrastructure to support the mineral activities as well as various restoration activities.  In addition, the Project area has been impacted by numerous forest fires.

These historical actions have changed the course, nature and quality of rivers and streams in the area, and left substantial surface disturbance, detrimental environmental impacts and residual surface features that persist to this day.

The mining history in this region of Idaho began in 1894 when the Caswell brothers began a sluice box operation in Monumental Creek in what is now known as the Thunder Mountain Mining District, located about ten miles east of Stibnite.  In 1902, a gold rush was underway to the Thunder Mountain District with associated development of roads and the creation of the town of Roosevelt.  By 1909, the gold rush was finished, and the town of Roosevelt flooded and was abandoned in the spring of that year after a mudslide blocked Monument Creek creating present‐day Roosevelt Lake.

During the Thunder Mountain gold rush, many prospectors had passed through the District, discovering mercury (east of the District), antimony, silver and gold, but no substantial mining activity occurred in the District until around 1917, when the World War I demand for mercury led to the development of several properties in the Cinnabar area, east of the present‐day Midas Gold Project area.

Two periods of major development and mining operations have occurred in the Stibnite area of the District: one from the late 1920s into the early 1950s and another from the late 1970s through the mid‐1990s.  District activity has principally occurred in three general locations: Hangar Flats, Yellow Pine and West End.  …

Hangar Flats Deposit

Gold and antimony mineralization were discovered in the Hangar Flats area around 1900, but development was slow given the remoteness of the area and the technical complexity involved with milling of refractory gold and antimony ores at the turn of the century.  When the lead up to and start of The Great War (World War I) caused an increased demand for metals, especially antimony, Albert Hennessy, who had studied the property a decade earlier, staked the first claims here in 1914.

In 1919, Albert Hennessy and his partners (who included J.J. Oberbillig, a Boise mining engineer and assayer, and J.L. Niday, a Boise lawyer) established the Meadow Creek Silver Mines Company and, in 1920, began initial (albeit minimal) underground development work on what would eventually become the Meadow Creek Mine in what is now referred to as the Hangar Flats area.

Meadow Creek Underground Mine

In 1920, the United Mercury Mines Company acquired the Meadow Creek Silver Mines Company with the intent to consolidate mining properties in the area.  This effort of property consolidation continued for the next several years, along with sporadic underground development work.

In 1925, Homestake Mining Company from Lead, South Dakota, optioned the Meadow Creek Mine property and conducted sampling and metallurgical investigations but decided to forego purchase after their metallurgists were unable to determine a suitable milling method for the gold‐antimony material.  With Homestake’s option dropped, the United Mercury Mines Company continued their underground development work during 1926.

In 1927, F.W. Bradley, a San Francisco mining engineer and President of the Bunker Hill & Sullivan Mining & Concentrating Company, optioned the Meadow Creek property, under an entity known as the Yellow Pine Company.  This company invested in a major expansion program, that included immediate improvements to the Meadow Creek mine camp and new facilities at the Meadow Creek Mine.

Bradley foresaw the need for a good access and service road into the Meadow Creek Mine site from Yellow Pine, one that could handle trucks to haul mine and mill equipment and supplies to the site, and also one that could be used for worker access. In 1928, construction started on a 12‐mile road that would parallel the East Fork of the South Fork of the Salmon River (EFSFSR), and would connect Yellow Pine to the mine site.  Bradley negotiated an agreement with the Forest Service, wherein Bradley funded 50% of a four‐and‐a‐half‐mile stretch of the new road through the EFSFSR canyon area south of Yellow Pine, and the US government financed the other 50%. The Yellow Pine Company funded and constructed the remainder of the road, moving north from the Meadow Creek Mine area.

Development work intensified in the Meadow Creek Mine in 1928, and a new adit, known as the North Tunnel (located approximately a mile and a half north of the Meadow Creek Mine portal) was started to follow the strike of the Meadow Creek fault. …

The year 1928 also saw the installation of a sawmill at the Meadow Creek Camp that provided lumber for underground activities and the construction of a new warehouse, machine shop, compressor building, bunkhouse, individual houses, and remodel and upgrade of existing camp buildings.  Sufficient supplies were brought to the site during the summer and fall of 1928 to allow development and construction activity to be conducted during the winter months.

In 1929, the road between Yellow Pine and the Meadow Creek Mine surface facilities was finished, and along this road, about a half mile north of the confluence of Fiddle Creek and the EFSFSR, the Yellow Pine Company began construction of a new surface camp (which became known as Monday Camp) that included mine support facilities and a large boarding house.  Nearby, the company started to drive two long adits, identified as: (1) the Monday tunnel, which would head southward in the Meadow Creek fault and (2) the Cinnabar tunnel, which would be driven eastward into the company’s gold and mercury deposits.

By 1930, underground development work within the Meadow Creek Underground Mine was well underway, and the mine had considerable surface facilities (including a small mill) to support the underground operations.

Photo 1, Meadow Creek Mine Camp (circa 1930)
Photograph courtesy of Robin McRae

Near the Meadow Creek Mine surface facilities, in a level area on the west side of the EFSFSR, an air strip was constructed that allowed passengers, mail and light supplies to be delivered to the site from the town of Cascade on a regular schedule from November through June. (*1)

(*1) Until 1941, the road from the town of Cascade into the site was closed during the winter; access to the site in the winter until that time was by snowshoes, dog sleds or ski‐equipped airplanes.  

Monday Camp

Work also continued in 1930 at the Monday Camp.  This included underground extension of both the Monday and Cinnabar tunnels. Additional surface facilities were constructed which included more housing, warehouse storage, a miner’s change facility, a machine shop, an assay office, post office, a compressor house, woodsheds, and oil‐fired furnaces

Photo 2, Monday Camp (circa 1931)
Photograph courtesy of Robin McRae.

A long trestle bridge was constructed across the EFSFSR to connect the portal areas of the Monday and Cinnabar tunnels; this allowed easier accessibility for workers and equipment across the EFSFSR

Photo 3, Trestle Bridge at Monday Camp (circa 1931)
Photograph courtesy of Robin McRae

To provide electric power for the existing and planned mine and expected mill facilities, the Yellow Pine Company installed a new 525 kW hydroelectric power plant on the south side of Sugar Creek near its confluence with the EFSFSR; the generator was driven by a Pelton water wheel, operating under a 520‐foot head.  Transmission lines were installed to distribute electric power to the site’s facilities.

A water retention dam was also constructed on the East Fork of Meadow Creek to create a reservoir to provide water for milling and for electric power generation for the mining and milling operations, the housing and other facilities at the Meadow Creek and Monday camps, and (eventually) for the community of Stibnite. To provide water to the power plant, an 11,000‐foot long, 28‐inch diameter redwood‐stave pipe, coupled with a 1,620‐foot long, 24‐inch diameter steel penstock, was installed (see Photo 4). Additional water retention structures were built at later dates at Garnet Creek, Hennessy Creek and in Fiddle Creek.

Photo 4, Water Delivery Pipeline for Power Plant on Sugar Creek (circa 1930)
Photograph courtesy of the J Nock family.

Also, during 1930, metallurgical testing continued at the Berkeley Laboratory in California to determine the best and most economic process to mill the gold‐silver‐antimony ore and, by the end of the year, the flotation process and testing was positive enough (and the Yellow Pine Company had developed sufficient ore at the Meadow Creek Mine) to justify the construction of a mill with the capacity to handle 150 tons of ore per day.

The year 1931 proved to be another busy year.  Underground mining continued at the Meadow Creek Mine and, to further support operations, a new cookhouse, bunkhouse, warehouse facilities and additional housing was constructed.  The biggest effort in 1931 was the construction and completion of the new mill, and, by year’s end, the milling of ore began (see Photo 5).

Photo 5, Meadow Creek Mill (circa 1931)
Photograph courtesy of Robin McRae.

In 1932, work ceased on the Monday and Cinnabar tunnels, and the primary focus of the Yellow Pine Company involved production from the Meadow Creek Mine. The mill capacity was increased to 200 tons of ore per day, with most of the mill concentrates being sold and transported to a smelter in Utah.  Mill tailings were being discarded in an area adjacent to the mill near the EFSFSR.  By year’s end, the Meadow Creek Mine had become the largest producer of antimony in the United States and the top gold producer in Idaho.

Throughout its life, the Meadow Creek Mine operated from six distinct underground levels with numerous drifts, crosscuts, raises, winzes, and stopes. In total, over 25,000 feet of underground workings were developed within the mine, with substantial subsurface exploration drilling as part of the operation.

From 1931 into 1938, the Meadow Creek Mine extracted gold, silver and antimony ore, which was milled at the adjoining Meadow Creek Mill. …

In early 1938, the Meadow Creek Mine was shut down, and ore production shifted to surface mining at the newly discovered Yellow Pine deposit. …

In 1943, an attempt was made to re‐open portions of the old Meadow Creek Mine workings to explore for antimony and tungsten in support of the war effort.  From 1943 to 1945, additional core drilling was completed in the mine. A small amount of tungsten mineralized material was reportedly extracted during this period from underground mine levels that had not caved or been abandoned.  After World War II, activity at the mine ceased, and the Meadow Creek Mine went dormant.

In 1949, Bradley raised the dam on the East Fork of Meadow Creek (the one built in 1931 to provide water for the hydroelectric power plant on Sugar Creek) to accommodate increased water demand created by the construction of a new smelter.

Photo 6, Reservoir on East Fork of Meadow Creek (circa 1950)
Photograph courtesy the J Nock family.

Defense Minerals Exploration Administration

As active mining ceased at the Yellow Pine pit in 1952, the Bradley Mining Company (BMC) was awarded two contracts by the Defense Minerals Exploration Administration (DMEA) and performed exploration work through 1955, both around the Yellow Pine Pit and north of the former Meadow Creek Mine.  The impetus for that work was provided by the Defense Production Act of 1950. It provided monetary assistance for companies to locate new reserves of strategic and critical minerals. If mineralized material was discovered, the companies that received assistance were required to reimburse the government from the proceeds of the operation. If no economic mineralization was discovered, the government loans were forgiven.

Through the DMEA program, BMC developed nearly 5,000 feet of underground workings with an associated adit and waste rock dump on the north extension of the Meadow Creek orebody, in three underground levels on the north side of the Hangar Flats Deposit. …  Underground mapping, sampling and drilling activities were conducted over the three‐year period, but this effect did not trigger the resumption of any mining from the Meadow Creek Mine.

Post 1960 Activity in Hangar Flats Area

After the completion of the DMEA program in 1955, there was no additional underground (or surface) mining activity in the Hangar Flats area, but there has been sporadic exploration activity.

In June 1965, more than a decade after the closure of the Stibnite Mill and Smelter, high runoff caused a catastrophic failure of the dam on the East Fork of Meadow Creek; the dam built in 1931 to provide water for the hydroelectric power plant on Sugar Creek (see Photo 7). Damage at the time was substantial, and the drainage remains a major source of sedimentation due to active, high‐flow head cutting and erosion.  The head cutting has also lowered the water table in the upper valley, reducing the quality of the wetlands in that area.  This area is now often referred to as Blowout Creek.

Photo 7, Failed Dam Site in East Fork of Meadow Creek (circa 2014)
Midas Gold collection

In the late 1970s, Ranchers Exploration Company (Ranchers) acquired interests in the area from BMC and completed a large soil grid over the trace of the Meadow Creek Fault system, including the area adjacent to the old Meadow Creek Underground Mine.  Ranchers’ work outlined a number of large gold‐in‐soil anomalies over the old underground mine area, along the trace of the Meadow Creek Fault system, and north to the Yellow Pine Deposit. Ranchers completed some trenching, but they did no drilling on the anomalies in this area; instead they focused their work on the Yellow Pine deposit.

In 1984, Hecla Mining Company (Hecla) merged with Ranchers and continued trenching and geophysical surveys, as well as drilling shallow reverse circulation (RC) holes in the area of the historical Meadow Creek Mine. Their trenching and RC drilling outlined a broad, but poorly‐defined zone of gold mineralization above the old workings and along strike to the north, as well as under the historical Stibnite Mill and Smelter complex along the base of the hill (where the Meadow Creek Mine adits were located).

In 1986‐7, under a toll processing agreement with Pioneer Metals Corporation (Pioneer), Hecla initiated a program to leach historical Bradley ore and waste rock stockpiles from the Yellow Pine Pit area at Pioneer’s leach pad complex. … Subsequently, Hecla constructed their own gold heap leach facility (principally over the site that was historically occupied by the Stibnite Mill and Smelter), and Hecla operated this heap leach facility from 1988 to 1992 (see Photo 11).  The ore for Hecla’s heap leach facility was mined from an area known as the “Homestake Pit”, an area adjacent to the historical Yellow Pine pit (within the footprint proposed new Yellow Pine pit), and was trucked to the heap leach facility.

Photo 11, Hecla Heap Leach Operation (circa 1991)
US Forest Service archive photo.

In the 1980s and 1990s, several mining companies operated heap leach gold and silver facilities in the area in the vicinity of the former Meadow Creek Mine, the Stibnite Mill and Smelter, and related facilities.  These other leach pads still exist but have been covered by fill.

In the mid‐1990s, Hecla’s heap leach processing facilities were decommissioned and removed, and the site was reclaimed; however, the Hecla heap leach pad and pile was left in place and remains visible today (see Photo 12).  After the early‐1990s, no new exploration or mining‐related activity occurred in the Hangar Flats area until Midas Gold began exploration work in 2009.

Photo 12, Hecla Heap (circa 2011)
Midas Gold files.

The U.S. Forest Service, Idaho Department of Lands (IDL), Idaho Department of Environmental Quality (IDEQ) and the U.S. Environmental Protection Agency (EPA) have performed several removal actions in this area, including removal of minor quantities of legacy tailings and the smelter stack in 2003, re‐channelization of lower Meadow Creek in 2005, … and covering certain legacy tailings‐related impoundments with clean fill in 2009. In spite of these actions, legacy tailings remain buried over much of the area, including under the airstrip and adjacent to Meadow Creek.

Yellow Pine Deposit

The Yellow Pine deposit (and subsequent mining activity) is located approximately two and half miles north of the Meadow Creek Mine; this deposit is situated north of the confluence of Midnight Creek and EFSFSR and south of the confluence of Sugar Creek and the EFSFSR. …

The first claims were staked in the area of the Yellow Pine deposit in 1923 by prospector Al Hennessy, who formed the Great Northern Mines Company with J. L. Niday.  Minimal work was completed on the deposit during the time period of 1926 through 1928; at the end of 1928, there were three adits in the general vicinity of the site, with a combined development length of less than 200 feet.  These adits were known as the North Tunnel, the Monday Tunnel and the Cinnabar Tunnel.

In 1929, the claims were optioned to F.W. Bradley’s Yellow Pine Company (predecessor to the Bradley Mining Company). The Yellow Pine Company constructed a road through this area to the Meadow Creek Mine, installed a pipeline and a hydroelectric power plant near the confluence of Sugar Creek and the EFSFSR, erected surface facilities and a housing camp on the west side of the confluence of Midnight Creek and the EFSFSR, and drove the aforementioned Monday and Cinnabar tunnels on opposing sides of the valley.  However, after 1932, the Yellow Pine Company did little additional work on the property, and instead focused on their mining and milling activities associated with the Meadow Creek Mine.

Yellow Pine Pit and Associated Activity

In 1933, J.J. Oberbillig purchased the claims in the area of the Yellow Pine deposit from the Great Northern Mines Company, and he immediately re‐optioned the claims to the Yellow Pine Company.

No activity occurred at the site until early 1937, when a leak in the redwood pipeline conveying water to Yellow Pine Company’s hydroelectric plan washed dirt and rock off the hill on the east side of the EFSFSR and exposed a mineralized zone that would eventually become the east side of the Yellow Pine Pit. This mishap led to BMC (successor to the Yellow Pine Company) developing short adits on both sides of the EFSFSR, from which exploration drilling was conducted. In the late summer of 1937, the BMC began mining ore material from the west side of the EFSFSR, at a site designated as the “West Quarry”, which would eventually become part of the larger Yellow Pine Pit.

During early 1938, the Meadow Creek Mine was shut down and, from mid‐1938, BMC shifted its entire mining focus to the Yellow Pine deposit. The EFSFSR was diverted in the area of mining, which eliminated fish passage up the EFSFSR (which has not been restored to this day). While the West Quarry was being mined and ore material being trucked to the Stibnite Mill (formerly the Meadow Creek Mill), the BMC conducted surface drilling exploration on the east side of the EFSFSR; this drilling revealed higher gold values than the West Quarry area, and nearly 600 feet of underground adits and crosscuts into the east area confirmed the surface exploration results.

In 1939, BMC’s operations were conducted from the area designated as the “East Quarry”, again in the area which would become part of the larger Yellow Pine Pit, and ore was hauled by trucks to the Stibnite Mill (formerly known as the Meadow Creek Mill), where construction was underway to expand the its capacity from 200 to 400 tons per day.

With the looming concern that the U.S. might be drawn into the war in Europe (World War II), the U.S. Congress passed and President Franklin Roosevelt signed the Strategic Materials Act in June of 1939.  This new law allowed the federal government to purchase mineral commodities that the Army and Navy Munitions Board had classified as strategic, and this Board designated both antimony and tungsten (two of the minerals prevalent in the Yellow Pine deposit) as strategic.

With the rising U.S. government interest in locating reserves of both antimony and tungsten, the U.S. Geological Survey (USGS) and the U.S. Bureau of Mines initiated separate sampling, mapping, trenching and drilling projects to investigate the Yellow Pine area.  The USGS concentrated on mapping, sampling and core logging, with a particular interest in tungsten.  The Bureau of Mines, in conjunction with BMC, began exploration and development drilling in the Yellow Pine deposit area.  This joint drilling program, one of many such joint programs over the next decade and a half, was originally prompted by 1939 Strategic Materials Act, and later expanded by the entry of the U.S. into World War II and later into the Korea War.

With the discovery of tungsten in 1941, the BMC expanded the Stibnite Mill to produce a tungsten concentrate, and mining intensified in the Yellow Pine pit to produce tungsten, antimony and gold ore, and haul this ore by truck to the mill (see Photo 14).

Photo 14, Yellow Pine Pit (circa 1943)
Photograph courtesy of the J Nock family.

Until 1942, mining was conducted on both the east and west sides of the EFSFSR, but, during this year, it became apparent that, if the Yellow Pine pit was to be expanded and deepened, a more efficient means to divert the EFSFSR had to be developed since the existing surface ditches constructed in 1938 to divert the EFSFSR were becoming inefficient. In late 1942 and into early 1943, the BMC drove a 3,500‐foot tunnel to divert the EFSFSR around the open pit to the east. The tunnel, which became known as the Bailey Tunnel, was driven by mining crews working from each end and measured about seven feet wide by nine feet high. The tunnel entrance was located on the east side of the EFSFSR while the tunnel outlet was located in the Sugar Creek drainage.  Upon completion, water was diverted into the tunnel to allow for Yellow Pine Pit expansion. (*2) (see Photo 15).

(*2) During the winter months and low flow conditions in the summer, BMC used the tunnel to facilitate removal of ore from underground workings beneath the open pit.

Photo 15, Bailey Tunnel: Diversion of EFSFSR into Sugar Creek (circa 1943)
Photograph courtesy James Collord.

Throughout the era of World War II, the BMC recognized the vital importance of antimony and tungsten to the war effort and was diligent to expand and upgrade the operation and efficiency of the Stibnite Mill.  New ball mills, additional flotation cells and miscellaneous auxiliary equipment were added to the milling circuit.  Tailings were initially dumped in the Meadow Creek valley downstream of the mill and, later, upstream of the mill (see Photo 16).

Photo 16, Stibnite Mill and Tailings Pond (circa 1943)
Photograph circa 1942, courtesy of James Collord.

Given its convenient location just south of the Yellow Pine Pit, the Monday Camp, which was originally installed in 1928 as a base area for driving the Monday and Cinnabar tunnels, was converted for use as a truck maintenance shop, machine shop, fuel storage facilities, and truck parking area (see Photo 17).

Photo 17, Monday Camp (circa 1944)
Photograph courtesy James Collord.

Throughout World War II, the BMC payroll ranged between 300 to 400 workers, and the population of the community Stibnite had grown to approximately 750 people.  The town site area included employee homes, a recreation center with a bowling alley, an auditorium for weekly movies and monthly dances, a hospital with surgical facilities (*3), a four‐room school, an automobile service station, a general store, a restaurant, and a municipal waste landfill.  Stibnite also featured a ski team and a high school football team (see Photo 18).

(*3) This was the first hospital in Valley County.

Photo 18, Stibnite Town Site (circa 1945)
Photograph courtesy James Collord.

Other “neighborhoods” existed in outside the main site for the town of Stibnite, including the Fiddle and Midnight neighborhoods (see Photo 19). The neighborhood of Fiddle is located in the lower Fiddle Creek Valley that is located slightly right of center in the photo, and the neighborhood of Midnight is found in the lower part of the photo, between the two pine trees.

Photo 19, Fiddle Creek and Midnight Creek Neighborhoods (circa 1945)
Photograph courtesy Robin McRae.

In 1943, electric power demands at the Stibnite Mill complex and the surrounding administrative and housing areas had risen beyond the capacity of the existing hydroelectric power plant. Electric power for the Stibnite Mill was supplemented with twelve diesel generators (with its related fuel haulage requirements), but electric power demand was nearing the site’s capacity.  Idaho Power Company began construction of a 106‐mile long electric transmission line to Stibnite, and, in 1944, the line was completed with the capacity of 66,000 volts of electricity.  This new line replaced the site’s hydroelectric plants and diesel generators as the primary source of electricity to the site, and allowed the capacity of the Stibnite Mill to reach 800 tons per day.

During the summer of 1945, the BMC installed a crushing plant in the open pit.  The ore passed through a jaw crusher, up a 500‐foot long conveyor to a cone crusher, and then up another 500‐foot conveyor to a secondary crusher and then to ore storage bins (*4) (see Photo 20).

(*4) The conveyor system was powered by a series of Pelton water wheels housed in the floors of the crushing buildings.  These Pelton wheels used water from Hennessy Creek.

Photo 20, Yellow Pine Pit (circa 1946)
Photograph courtesy Robin McRae.

In the fall of 1946, a new rod mill was added to the Stibnite Mill, which increased its capacity from 800 tons per day to 1,800 tons per day.  Later in the year, additional infrastructure was added to the mill that further boosted capacity to 2,400 tons per day.

By 1946, tailings disposal had become a logistical problem (*5).  The Bradley Mining Company was running out of room to discharge tailings adjacent to the mill, and the EFSFSR was being subjected to ever increasing sedimentation and turbidity from leakage and overflow from the existing tailings impoundments.

(*5) Before 1946, mill tailings were simply discarded into impoundments west of the mill or discharged directly into Meadow Creek.

During 1946, to alleviate this situation, the BMC constructed a large embankment west of the mill to create a storage area that was nearly a mile long and approximately 1,400 feet across at its widest point.  In conjunction with the expanded tailings storage area, the company dug a one‐mile long diversion canal (*6) to divert Meadow Creek around the south side of the new tailings facility and added a down gradient secondary settling basin to aid in the clarification of water being discharged from the tailings storage area before its release into Meadow Creek.

(*6) In 1959, the Forest Service ordered the BMC to breach the Meadow Creek diversion; this action allowed Meadow Creek to resume a more natural course through the tailings.  However, over the next 25 years, an estimated 10,000 cubic yards of tailings were eroded and carried downstream.  In 1998, contractors for Mobil Oil Corporation, the successor to one of the former mine operators, constructed a new channel around the SODA and the USFS completed that project.  In 2005, contractors working for state and federal agencies constructed a new channel around the lower Meadow Creek legacy tailings disposal site to re‐route Meadow Creek around the tailings in this area.

From 1946 to 1952, the Bradley Mining Company deposited an estimated 4 million cubic yards of mill tailings into this new tailings disposal facility (see Photo 21).  Note that the disposed tailings are found in the upper part of the photo, above the mill complex.

Photo 21, Stibnite Mill and Tailings (circa 1948)
Photograph courtesy of James Collord

In 1947, after being the top U.S. producer of primary antimony for nearly a decade and with existing smelters having difficulty in recovering antimony and gold from the Stibnite Mill concentrates, combined with rising costs for transportation of concentrates from the site, the BMC decided to invest in the design and construction of an on‐site antimony smelter adjacent to the Stibnite Mill (see Photo 22 and Photo 23).  This project required new housing for construction crews and added employees.

Photo 22, Antimony Smelter under Construction (circa 1948)
Photo from “History of the Stibnite Mining Area, Valley County, Idaho.”  Report prepared by Victoria E. Mitchell of Idaho Geological Survey, dated April 2000.

Photo 23, Completed Antimony Smelter (circa 1949‐50)
Photo from “History of the Stibnite Mining Area, Valley County, Idaho.”  Report prepared by Victoria E. Mitchell of Idaho Geological Survey, dated April 2000.

The BMC continued to haul ore material from the Yellow Pine Pit for milling and smelting at its Meadow Creek facilities (see Photo 24).

Photo 24, Ore Haulage to Stibnite Mill and Smelter (circa 1950)
USFS archive photo.

With the start of the Korean War, the BMC intensified its exploration efforts to locate additional tungsten resources.  The in‐pit crusher was moved, allowing the company to mine the remnant tungsten ore body beneath it.  In 1951, the company set up a 2,000‐cubic‐yard‐per‐day placer plant to reprocess tailings that had been released downstream of the Meadow Creek Mill that had mixed with alluvial gravels and to recover scheelite (tungsten ore) from the glacial till and gravels between the crest of the pit highwall on the north side of the pit and the confluence between the EFSFSR and Sugar Creek (see Photo 25).

Photo 25, Tungsten Placer Operation (circa 1951)
Photograph courtesy of the DeMoss Family.

In 1952, the Yellow Pine Pit was more than 450 feet deep, with 40 to 80‐foot‐high benches.  Ore was being mined at a rate of 2,500 tons per day, with an ore‐to‐waste rock ratio of 1:1½.  The BMC was also awarded a government‐sponsored exploration program authorized by the Defense Minerals Exploration Administration under the Defense Production Act of 1950 that allowed this agency to provide economic support (generally 50 to 75% of the costs) to locate reserves of strategic and critical minerals. This government program did not change lack of demand or the price for antimony in 1952, which plummeted from nearly $0.52/pound in January to $0.36/pound at the end of the year.  In response to lack of demand and falling antimony prices, operations at the Yellow Pine Pit were suspended in June of 1952; the Stibnite Mill ceased operations in July; and the Stibnite Smelter was shut down in August.

The Yellow Pine Pit had operated continuously for nearly 14 years. …

After 1952, the Yellow Pine Pit was never re‐activated.

The EFSFSR diversion tunnel around the Yellow Pine Pit was abandoned, and flow from the EFSRSR was allowed to cascade into the abandoned pit, forming a pit lake. Despite the renewed flow down the valley, the un‐reclaimed highwall on the south side of the Yellow Pine Pit remained as a continuing barrier to fish passage (replacing that presented by the original diversion channel constructed by BMC in 1938 and later by the BMC water diversion tunnel installed in 1942) into the upper reaches of the EFSFSR and Meadow Creek (see Photo 26).

Photo 26, Yellow Pine Pit (circa 2014)
Midas Gold collection

For several years after pit closure, the BMC conducted sporadic and limited contract milling and smelting from ore shipped into the site from mines external to the District; however, this activity proved uneconomic, and, in 1958, the smelter was dismantled and removed from the site.

Most residents left the community of Stibnite after operations ceased in 1952.  The town continued to exist for a short time, but with a continued dwindling number of residents. In the mid to late 1950s, many of the abandoned Stibnite houses were moved to Cascade and McCall, but the mill and mine support facilities, along with the remaining Stibnite houses and facilities were simply left to the elements of nature (see Photo 27 and Photo 28).  Through the years, remaining structures at the site were stripped of metal, burned on site and buried under a thin layer of cover material.  Nothing remains visible of the old Stibnite town, mill or smelter today, except for a few foundations.  The remains of two structures that housed the in‐pit crushers remain visible in the abandoned Yellow Pine pit.

Photo 27, Abandoned Meadow Creek Mill Site (circa 1978)
Photo courtesy of Sharon McConnel

Photo 28, Abandoned Stibnite Recreation Center (circa 1978)
Midas Gold collection.

Post 1960 Activity at Yellow Pine Deposit

After the closure and removal of the Stibnite Smelter in 1958, no substantial exploration was conducted at the site until the 1970s, when Ranchers and, later, its successor, Hecla, conducted drilling campaigns on the Yellow Pine Deposit that continued through the mid‐1990s.  This drilling was supplemented with trenching and geologic mapping, coupled with engineering, environmental and metallurgical studies.  The 1970s brought an interest in low grade oxide mineral deposits from which gold could be extracted using the heap leach extraction method developed by the U.S. Bureau of Mines.

From 1988 to 1992, Hecla developed a surface pit in an area, known as the “Homestake Pit”, which was adjacent to the old Yellow Pine Pit and that lies within the footprint of the proposed new and expanded Yellow Pine pit (see Photo 29).  This pit provided oxide material for Hecla’s heap leach operations that were located at the site of the surface facilities used for the historical Meadow Creek and Yellow Pine mines.

Hecla recovered gold from the Homestake pit and associated heap leach operations. …  Note the abandoned Yellow Pine Pit (and pit lake) in the upper right part of the photo.

Photo 29, Homestake Pit (circa 1991)
Midas Gold collection

In the early 1990s, American Barrick Resources (Barrick) optioned the property; in a joint venture with Hecla, Barrick completed additional drilling and metallurgical test work before dropping the option.  In the late 1990s, Hecla relinquished its control of the property back to the Bradley estate interests after closure and reclamation of the operations at the Homestake Pit and associated heap leach facilities.

In 2003, Vista Gold Corp. acquired an option on the Yellow Pine Deposit from BMC and completed an independent mineral resource estimate and preliminary assessment of the site, but this firm did not undertake any exploration drilling work on the site.  No additional exploration activity was conducted at the Yellow Pine Deposit until Midas Gold acquired their interests from Vista Gold’s subsidiary Idaho Gold LLC in 2011.

West End Deposit

Gold mineralization was first discovered along the West End Fault by BMC in the late 1930s or early 1940s; during this time BMC’s exploration focused on replacement of reserves at their Yellow Pine operation.  Subsequent work, sponsored by the USGS, outlined a large biogeochemical and soil anomaly that led to follow‐up by Canadian Superior Mining (U.S.) Ltd. (Superior), and its successors.  A modern era of exploration and development stretched from the mid‐1970s to the mid‐1990s, prompted primarily by the rise in gold prices and the development of the aforementioned heap‐leach oxide gold recovery methods.

Superior conducted geological, geophysical, and geochemical investigations from 1974 to 1977 to evaluate the potential for heap‐leach oxide gold and silver in the West End and adjacent Stibnite deposit (now collectively known as West End Deposit). In 1979, Superior Oil Company, Canadian Superior’s parent company, purchased Superior’s outstanding shares and became sole owner of the West End Deposit, referred to as the West End Mine. After completion of an Environmental Impact Statement and the issuance of a favorable Record of Decision by the Forest Service, a 2,000‐3,000 ton‐per‐day (tpd) open pit oxide mining operation began in 1982 (see Photo 30).

Photo 30, West End Pit (circa mid 1990s)
USFS archive photo

Superior installed a gold leaching process plant (see Photo 31) and constructed five “on‐off” heap‐leach pads on the west side of the EFSFSR, and north of the historical Stibnite Mill area. …  Between 1982 and 1996, Superior (and its successors) hauled oxide material from the West End Mine to the leach pad site, crushed this material, and placed it on one of the five lined pads.

Photo 31, Canadian Superior Heap Leach Process Plant (circa 1984)
Source: USFS archive photo

After the ore material was leached with a cyanide solution to recover gold, the material was neutralized and rinsed and became what miners call “spent ore”.  Superior (and its successors) removed this spent ore from the pads and hauled it for permanent placement over historical Stibnite Mill tailings (*7) that had been discarded into the upper Meadow Creek valley west of the now abandoned Stibnite Mill and Smelter.  Superior (and their successors) placed more than six million tons of spent ore in this location, which is commonly referred to as the Spent Ore Disposal Area (SODA); …

(*7) The Yellow Pine Mining Company and the BMC placed more than 4 million cubic yards of tailings materials in this area.  The majority of the legacy tailings are now located below the alluvial water table.  In addition, the upstream wetland, located west of the legacy tailings and SODA (formerly a water storage area related to Bradley’s operations), is also underlain by tailings.

As part of its spent ore disposal activity, Superior also constructed a new diversion channel to route Meadow Creek around the south side of the SODA.  Upon completion of gold and silver heap leach and processing activities, which included disposal of spent ore, the processing area, leach pads, and SODA area were reclaimed and seeded (see Photo 36).

Photo 36, Spent Ore Disposal Area (circa 2014)
Midas Gold collection

In 1984, Mobil Oil Corporation (Mobil) purchased Superior Oil, and, in 1985, suspended mining at the West End Mine; however, the heap leach processing of previously mined material continued.

In 1986, Pioneer Metals Corporation (Pioneer) purchased the West End Mine from Mobil and re‐initiated mine operations and exploration activity, which continued until 1991, after which the site went through a series of owners and operators: Pegasus Gold Corporation (1992), MinVen Gold Corporation, later changed to Dakota Mining Company (1993), and Dakota Mining Company’s subsidiary company, Stibnite Mine Inc. (SMI), from 1994 until 1996.

During 1994‐1996, SMI conducted sporadic drilling and development of the West End Mine, including a small area on the east side of the West End Deposit known as the Stibnite Pit and a small pit, known as the Garnet Creek Pit (see Photo 37), located approximately 1.5 miles to the south of the Stibnite Pit.  The Stibnite and Garnet Creek Pits were short‐lived open pit mines. Ore material removed from the Stibnite and Garnet Creek Pits were leached on the Superior on‐off leach pads.

Photo 37, Garnet Creek Pit in 1997
USFS archive photo

Gold and silver were produced from the West End Deposit from 1982 to 1996. … There has been no mining activity at the West End Deposit since 1996.

source: Appendix D History of the Stibnite Mining District
Midas Gold: Stibnite Gold Plan of Operations EIS

page updated September 1, 2020