Copper mining in Michigan

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Cupriferous amygdaloidal basalt, "Shot copper." Wolverine Mine, Kearsarge, Michigan. Cupriferous amygdaloidal basalt (Mesoproterozoic, 1.05-1.06 Ga; Wolverine Mine, Kearsarge, Upper Peninsula of Michigan, USA) (17323753605).jpg
Cupriferous amygdaloidal basalt, "Shot copper." Wolverine Mine, Kearsarge, Michigan.

In Michigan, copper mining became an important industry in the 19th and early 20th centuries. Its rise marked the start of copper mining as a major industry in the United States.

Contents

Geology

Mohawkite nugget, a mixture of domeykite, algodonite and native copper Mohawkite.jpg
Mohawkite nugget, a mixture of domeykite, algodonite and native copper
Native copper nugget from glacial drift, Ontonagon County, Michigan. An example of the raw ore worked by Native Americans of the Old Copper Complex, 4000 to 1000 BCE. Copper-38278.jpg
Native copper nugget from glacial drift, Ontonagon County, Michigan. An example of the raw ore worked by Native Americans of the Old Copper Complex, 4000 to 1000 BCE.

Within the state of Michigan, copper is found almost exclusively in the western portion of the Upper Peninsula, in an area known as the Copper Country. The Copper Country is highly unusual among copper-mining districts, because copper is predominantly found in the form of pure copper metal ( native copper ) rather than the copper oxides or copper sulfides that form the copper ore at almost every other copper-mining district. The copper deposits occur in rocks of Precambrian age, in a thick sequence of northwest-dipping sandstones, conglomerates, ash beds, and flood basalts associated with the Keweenawan Rift.

The native copper deposits originate in fissures, steeply dipping veins or in the amygdaloid top portion of the Portage Lake Lava Series lava tops and conglomerate beds. This series of lava "is at least 15,000 feet thick in the Michigan copper district" and consists of "several hundred flood basalt flows." The district rocks are Precambrian in age and belong to the Keweenawan Series. The first six years of mining exploited the fissure deposits, then gave way to the amygdaloidal deposits. [1] :306,308

Although native copper was the dominant ore mineral, chalcocite (copper sulfide) was sometimes present, and, especially in the Mohawk mine, copper arsenide minerals such as mohawkite and domeykite. Gangue minerals included calcite, quartz, epidote, chlorite, and various zeolites. A number of copper mines also contained a notable amount of silver, both in native form and naturally alloyed with the copper. Halfbreed is the term for an ore sample that contains the pure copper and pure silver in the same piece of rock; it is only found in the native copper deposits of the Upper Peninsula of Michigan. [2]

Native American

Copper knife, spearpoints, awls, and spade made from copper deposits mined by Native Americans in Wisconsin from the Late Archaic period, 3000 BC-1000 BC. Copper knife, spearpoints, awls, and spud, Late Archaic period, Wisconsin, 3000 BC-1000 BC - Wisconsin Historical Museum - DSC03436.JPG
Copper knife, spearpoints, awls, and spade made from copper deposits mined by Native Americans in Wisconsin from the Late Archaic period, 3000 BC-1000 BC.

Native Americans were the first to mine and work the copper of Lake Superior and the Keweenaw Peninsula of northern Michigan between 5000 BCE and 1200 BCE. The natives used this copper to produce tools. Archaeological expeditions in the Keweenaw Peninsula and Isle Royale revealed the existence of copper producing pits and hammering stones which were used to work the copper. [3] Some authors have suggested that as much as 1.5 billion pounds of copper was extracted during this period, but some archaeologists consider such high figures as "ill-constructed estimates" and that the actual figure is unknown. Archaeologist Susan Martin wrote that "“The competent excavation of many prehistoric archaeological sites in the Lake Superior basin reveals the continuous use of copper throughout the prehistoric time range, in association with all of the other items of material culture (projectile points, pottery and the like) that are without a doubt the products of native technologies. Many of these sites have been dated reliably by radiocarbon means.... Clearly, copper-working continues up until the years of aboriginal contact with seventeenth-century Europeans. The speculators could at least acknowledge these facts rather than pretend that the association of copper with indigenous people doesn’t exist.” [4]

By the time the first European explorers arrived, the area was the home of the Chippewa people, who did not mine copper. According to Chippewa traditions, they had much earlier supplanted the original miners. The first written account of copper in Michigan was given by French missionary Claude Allouez in 1667. He noted that Indians of the Lake Superior region prized copper nuggets that they found there. [5] Indians guided missionary Claude Dablon to the Ontonagon Boulder, a 1.5-ton piece of native copper along the Ontonagon River. When American prospectors arrived in the 1840s, pieces of copper were found in streams or on the ground.

Douglass Houghton's 1841 copper report, followed by the Treaty of La Pointe in 1843, the publicity of the Ontonagon Boulder back east, and a federal mineral land office at Copper Harbor kicked off the mine rush. [6]

The copper pits abandoned by Native Americans led early miners to most of the first successful mines. "All the principal ore deposits were thus known before 1900, and each was discovered in exposures at or close to grass roots." [1] :306

Modern mining industry

Mid-19th century Cornish miners worked in the mines of the "Copper Belt" of the Keweenaw Peninsula of the Upper Peninsula of Michigan Cornish miners - 1866.png
Mid-19th century Cornish miners worked in the mines of the "Copper Belt" of the Keweenaw Peninsula of the Upper Peninsula of Michigan
Miners at the Tamarack Mine in the Copper Country of Michigan in 1905. TamarackMiners CopperCountryMI sepia.jpg
Miners at the Tamarack Mine in the Copper Country of Michigan in 1905.
Copper being loaded onto a steamer in Houghton, Michigan, c1905 Loading copper, Houghton, Michigan, c1905.jpg
Copper being loaded onto a steamer in Houghton, Michigan, c1905
Michigan mined copper production Michigan Copper Production.png
Michigan mined copper production

The Michigan State Geologist Douglass Houghton (later to become mayor of Detroit) reported on the copper deposits in 1841, which quickly began a rush of prospectors.

Mining took place along a belt that stretched about 100 miles southwest to northeast through Ontonagon, Houghton, and Keweenaw counties. [1] [6] :16–17 Isle Royale, on the north side of Lake Superior, was extensively explored, and a smelter built, but no mining of any importance took place there. [7] Some copper mineralization was found in Keweenawan rocks farther southwest in Douglas County, Wisconsin, but no successful mines were developed there.

Copper mining in the Upper Peninsula boomed, and from 1845 until 1887 (when it was exceeded by Butte, Montana) the Michigan Copper Country was the nation's leading producer of copper. In most years from 1850 through 1881, Michigan produced more than three-quarters of the nation's copper, and in 1869 produced more than 95% of the country's copper. [8]

Fissure veins

Commercial production began in 1844 at the Phoenix mine. Most early miners began with little knowledge or planning, and few mines ever saw production, much less profit. The first successful copper mine, the Cliff mine, began operations in 1845, and many others quickly followed. These first mines worked copper-filled fissure veins that cut across stratigraphic layers. [1] :306

Although the copper-mining region stretched about 100 miles from northeast to southwest, the most productive early mines, working fissure veins, were those at the north end in Keweenaw County (such as the Central, Cliff, and Phoenix mines), or at the south end in Ontonagon County (such as the Minesota Mine).

In Keweenaw County, the fissure lodes were nearly vertical mineralized zones with strike nearly perpendicular to that of the enclosing basalts and conglomerates. In Ontonagon County, by contrast, the fissures had strikes nearly parallel to, and dips slightly steeper than, the surrounding beds.

The miners sometimes found masses of native copper up to hundreds of tons. To extract a single mass of copper, miners could spend months chiseling it into pieces small enough to hoist out of the mine. Although they were pure copper, removing the masses took a great deal of effort, and was sometimes not even profitable. The majority of the copper recovered was "barrel copper" (pieces broken from the rock and hand sorted in the "rock house," and shipped to the smelter in barrels), and finer copper broken loose from the rock in stamp mills and separated by gravity in "buddles" or "jigs."

Stratiform deposits

USA Michigan location map.svg
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White Pine mine
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Central mine
Copper mining in Michigan

In the 1850s, mining began on stratiform native copper deposits in felsite-pebble conglomerates and in the upper zones of basalt lava flows (locally called amygdaloids). Although amygdaloid and conglomerate deposits tended to be lower-grade than the fissure deposits, they were much larger, and could be mined much more efficiently, with the ore blasted out, hoisted to the surface, and sent to stamp mills located at a different site. Amygdaloid and conglomerate mining turned out to be much more productive and profitable than fissure mining, and the majority of highly successful mines were on amygdaloid or conglomerate lodes. The first mine to successfully mine a stratiform ore body was the Quincy Mine in 1856.

The most productive deposit, the Calumet conglomerate, was opened by the Calumet and Hecla mining company in 1865. "Large scale production ceased in 1939." [1] :306

While the most successful fissure mines had been at the north and south ends of the district, the conglomerate and amygdaloid mines, which produced the great majority of Michigan copper, were concentrated in the center of the district, almost all in Houghton County. The most productive conglomerate and amygdaloid mines were located along a strip about two miles (3.2 km) wide and 24 miles (39 km) long, from the Champion mine on the southwest to the Ahmeek mine on the northeast, passing through the towns of Houghton, Hancock, and Calumet.

In the early 20th century, copper companies began to consolidate. With very few exceptions, such as the Quincy Mine at Hancock, the mines in the Copper Country came under the control of two companies: the Calumet and Hecla Mining Company north of Portage Lake, and Copper Range Company south of Portage Lake.

Annual production peaked in 1916 at 266 million pounds (121,000 metric tons) of copper. Most mines closed during the great depression as a result of depressed copper prices. Many mines reopened during World War II, when wartime demand pushed copper prices higher. The end of the war brought an end to high prices, and nearly all companies closed, leaving only the Calumet and Hecla, Quincy, and Copper Range mining companies. Both Calumet and Hecla and Quincy survived largely by reprocessing the stamp sand left from older mining operations, leaching out copper left by more primitive processing techniques. [9]

By 1968 the formerly great Calumet and Hecla was purchased by Universal Oil and became the company's Calumet division. By this time the Calumet and Hecla's original conglomerate workings had been abandoned and stamp sand reclamation had ended. The mines did not even produce enough copper to supply the company's internal demand. [10] The company opened several new shafts and dewatered several old ones in hopes of finding additional wealth, but none were successful. Later that year, Calumet and Hecla's mine workers went out on strike, and the new owners closed the mines for good. Only the Copper Range company's White Pine mine remained open, and its ore was mostly copper sulfides, rather than native copper. Michigan's native copper industry was essentially dead, after producing 11 billion pounds (5.0 million metric tons) of copper. [11]

Several companies attempted to reopen copper mines during the next two decades, including attempts by the Homestake Mining Company. None of these attempts lasted more than a couple of years or proved profitable.

Economic and environmental impact

The copper industry was, for over 100 years, the life blood of the Copper Country. The town of Red Jacket (now Calumet) used a portion of its budget surplus to build The Calumet Theatre, an opulent opera house which hosted famous plays and acts from across the world. Many wealthy mine managers built mansions which still line the streets of former mining towns. Some towns which existed primarily due to copper mining include Calumet, Houghton, Hancock, and Ontonagon. As the mines began to close, the Copper Country lost its major economic base. The population declined sharply as miners, shop owners, and others supported by the industry left the area, leaving many small ghost towns along the mineral range.

Tourism, education, and logging are now the major industries. The copper industry left many abandoned mines and buildings across the Copper Country. Some of these are now part of the Keweenaw National Historical Park. Some mines, such as the Adventure mine, Quincy Mine, and the Delaware mine, are open as tourist attractions. Many other mining lands are simply left abandoned.

Copper mining also took a significant impact on the environment. Mine rock processing operations left many fields of stamp sand, some of which grew so large as to become hazards to navigation in the Keweenaw Waterway. Most of these sterile sands are now superfund sites which are slowly being rehabilitated. Mines also required a great deal of wood, for supports in mine tunnels, housing, and steam generation. Virtually every part of the Copper Country was cleared of timber, to the extent that only a few small areas of old-growth forest like (the Estivant Pines) are left. Formerly cleared lands have been left to regrow, to the extent that many parcels of land are now being harvested on a limited basis by timber and paper companies.

White Pine mine

Spectacular specimen of elongated, spinel-twinned copper crystals from the old White Pine mine. Copper-60829.jpg
Spectacular specimen of elongated, spinel-twinned copper crystals from the old White Pine mine.

The copper-bearing Nonesuch Shale at the south end of the Copper Country in Ontonagon County had been known since the 1800s. But the ore grades were too low, the ore mineral particles too small, and the copper was largely in sulfides instead of native copper. All these conditions made the shale deposits uneconomical, although repeated attempts were made to mine the shale at the Nonesuch Mine.

In 1955 the Copper Range Company began large-scale mining at the White Pine mine, near the old Nonesuch mine. The deposit is a stratiform deposit in the lower 15 m of the Proterozoic Nonesuch Shale and the upper 2 m of the underlying Copper Harbor Conglomerate. The principal ore mineral was chalcocite, although native copper predominated in the lower part of the beds. The mine was very successful, producing more than 1.8 million metric tons (4.0 billion pounds) of copper during its life.[ citation needed ] The White Pine mine, the last major copper mine in Michigan, shut down in 1995. [12]

The company applied to government agencies to continue mining by in-situ leaching, using sulfuric acid to recover an additional 900 million pounds (410,000 metric tons) of copper by SX-EW. The Michigan Department of Environmental Quality approved the permit in May 1996, and White Pine installed a pilot in-situ leaching project. [13] Native Americans of the Bad River Indian Reservation in northern Wisconsin blockaded rail shipments of sulfuric acid to the mine (see Bad River Train Blockade ); the mine began receiving acid shipments by truck. The U.S. Environmental Protection Agency (EPA), which had previously held that it had no role in the permitting, reversed itself, and stated that White Pine would have to apply for a federal permit. White Pine, which had already started to recover copper from the pilot project, suspended solution mining in October 1996, and applied for to the EPA for the permit. [14] In May 1997 the company withdrew the EPA permit application, saying that further permitting delays had made the project uneconomical, and announced plans to begin reclamation of the mine site.

The tailings impoundment at the White Pine Mine is presently the site of significant environmental degradation. The University of Montana undertook extensive efforts to restore and revegetate the barren landscape from 1997 to 1999, but it is unclear whether this has been successful. The university has published a detailed report of its project. [15] Satellite images are available at ( 46°47′17.91″N89°31′47.97″W / 46.7883083°N 89.5299917°W / 46.7883083; -89.5299917 ).

In 2012, SubTerra used the mine for pharmaceutical research. [16]

The July 7th 2021 edition of the local news outlet Keweenaw Report has the headline: Mining set to return to White Pine. [17]

Eagle Mine

In addition to sedimentary copper ores that dominate the Upper Peninsula, Eagle Mine is a high-grade magmatic nickel-copper (Ni-Cu) sulfide-bearing deposit discovered by Rio Tinto in 2002 and later sold to Lundin Mining (2013). Eagle Mine is located on the Yellow Dog Plains, about 25 miles northwest of Marquette, in Michigan's Upper Peninsula. Construction work started in 2010, with commercial production commencing 2014 [18] and anticipated to last up to nine years. After mining is finished the site will be reclaimed. The mine is expected to produce 360 million pounds of nickel, 295 million pounds of copper and small amounts of other metals over its nine-year mine life (2014 to Q4 2023). Other base metals include platinum, palladium, and cobalt. Ores will be processed at the Humboldt Mill in Michigamme Township. The concentrate is loaded into covered train cars and shipped to smelters in either Canada or Europe.

Eagle Mine was the first operation to be permitted under Michigan's Non-Ferrous Metallic Mining Law, better known as Part 632.

Copperwood Mine

On March 13, 2013, the Michigan Department of Environmental Quality (DEQ) issued Orvana Corporation, of Toronto, Ont. final permits to begin mining north of Wakefield, in Gogebic County. [19]

Orvana estimates that approximately one billion pounds of copper are present at their site, along with smaller quantities of silver. Studies indicate that 800 million pounds (360,000 metric tons) of copper can be extracted, as well as 3,456,000 ounces of silver. Production would last 13 years, based on those reserves. [20] The project was then bought by Highland Copper Company, a Montreal-based exploration company in 2014 and an updated feasibility report is underway and permits for the project are forthcoming by the end of 2018.

Back Forty Mine

The Back Forty Mine is a proposed open-pit metallic sulfide mine targeting gold and zinc deposits in Menominee County in the South Central part of Michigan's Upper Peninsula next to the Menominee River.

See also

Related Research Articles

<span class="mw-page-title-main">Hancock, Michigan</span> City in Michigan, United States

Hancock is a city in the Upper Peninsula of the U.S. state of Michigan. The population of Hancock was 4,501 at the 2020 census. The city is located within Houghton County, and is situated upon the Keweenaw Waterway, a channel of Lake Superior that cuts across the Keweenaw Peninsula. Hancock is located across the Keweenaw Waterway from the city of Houghton, and is connected to that city by the Portage Lake Lift Bridge. The city is located within Michigan's Copper Country region.

<span class="mw-page-title-main">Ontonagon County, Michigan</span> County in Michigan, United States

Ontonagon County is a county in the Upper Peninsula of the U.S. state of Michigan. As of the 2020 census, the population was 5,816, making it Michigan's third-least populous county. The county seat is Ontonagon. The county was set off in 1843, and organized in 1848. Its territory had been organized as part of Chippewa and Mackinac counties. With increasing population in the area, more counties were organized. After Ontonagon was organized, it was split to create Gogebic County. It is also the westernmost county in United States that lies within the Eastern Time Zone.

The Keweenaw Peninsula is the northernmost part of Michigan's Upper Peninsula. It projects into Lake Superior and was the site of the first copper boom in the United States, leading to its moniker of "Copper Country." Its major industries are now logging and tourism, as well as jobs related to Michigan Technological University.

<span class="mw-page-title-main">Copper Country</span> Region in the Upper Peninsula of Michigan, US

The Copper Country is an area in the Upper Peninsula of Michigan in the United States, including Keweenaw County, Michigan, Houghton, Baraga and Ontonagon counties as well as part of Marquette County. The area is so named as copper mining was prevalent there from 1845 until the late 1960s, with one mine continuing through 1995. In its heyday in the latter half of the 19th century and the early 20th century, the area was the world's greatest producer of copper.

<span class="mw-page-title-main">Minesota Mine</span>

The Minesota Mine is a former copper mine near Rockland, Ontonagon County in the Upper Peninsula of the U.S. state of Michigan. The Minesota was one of the most productive and famous early mines in the Michigan Copper Country.

<span class="mw-page-title-main">Quincy Mine</span> United States historic place

The Quincy Mine is an extensive set of copper mines located near Hancock, Michigan. The mine was owned by the Quincy Mining Company and operated between 1846 and 1945, although some activities continued through the 1970s. The Quincy Mine was known as "Old Reliable," as the Quincy Mine Company paid a dividend to investors every year from 1868 through 1920. The Quincy Mining Company Historic District is a United States National Historic Landmark District; other Quincy Mine properties nearby, including the Quincy Mining Company Stamp Mills, the Quincy Dredge Number Two, and the Quincy Smelter are also historically significant.

<span class="mw-page-title-main">Native copper</span> Mineral (as opposed to the chemical element)

Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native copper was an important ore of copper in historic times and was used by pre-historic peoples.

<span class="mw-page-title-main">Keweenaw National Historical Park</span> U.S. national historical park in Michigan

Keweenaw National Historical Park is a unit of the U.S. National Park Service. Established in 1992, the park celebrates the life and history of the Keweenaw Peninsula in the Upper Peninsula of the U.S. state of Michigan. As of 2009, it is a partly privatized park made up of two primary units, the Calumet Unit and the Quincy Unit, and 21 cooperating "Heritage Sites" located on federal, state, and privately owned land in and around the Keweenaw Peninsula. The National Park Service owns approximately 1,700 acres (690 ha) in the Calumet and Quincy Units. Units are located in Baraga, Houghton, Keweenaw, and Ontonagon counties.

<span class="mw-page-title-main">National Register of Historic Places listings in Houghton County, Michigan</span>

This is a list of the National Register of Historic Places listings in Houghton County, Michigan.

<span class="mw-page-title-main">Calumet and Hecla Mining Company</span>

The Calumet and Hecla Mining Company was a major copper-mining company based within Michigan's Copper Country. In the 19th century, the company paid out more than $72 million in shareholder dividends, more than any other mining company in the United States during that period.

<span class="mw-page-title-main">Copper Range Company</span>

The Copper Range Company was a major copper-mining company in the Copper Country of Michigan, United States. It began as the Copper Range Company in the late 19th century as a holding company specializing in shares in the copper mines south of Houghton, Michigan. The company was bought by Louisiana Land and Exploration in 1977.

<span class="mw-page-title-main">Nonesuch Mine</span>

The Nonesuch Mine is an abandoned copper mine and small ghost town in the southeast corner of the Porcupine Mountains State Park in Carp Lake Township, Ontonagon County, near Silver City, Michigan, United States. The area was given its name soon after Ed Less discovered the Nonesuch vein of copper on the Little Iron River in 1865. The name refers to the occurrence of the copper in sandstone: "nonesuch" ore existed elsewhere in the Copper Country.

The Copper Country strike of 1913–1914 was a major strike affecting all copper mines in the Copper Country of Michigan. The strike, organized by the Western Federation of Miners, was the first unionized strike within the Copper Country. It was called to achieve goals of shorter work days, higher wages, union recognition, and to maintain family mining groups. The strike lasted just over nine months, including the Italian Hall disaster on Christmas Eve, and ended with the union being effectively driven out of the Keweenaw Peninsula. While unsuccessful, the strike is considered a turning point in the history of the Copper Country.

<span class="mw-page-title-main">Nonesuch Shale</span>

The Nonesuch Shale is a Proterozoic geologic formation that outcrops in Michigan and Wisconsin, United States, but has been found by drill holes to extend in the subsurface as far southwest as Iowa.

<span class="mw-page-title-main">Cliff mine</span>

The Cliff mine was the first successful copper mine in the Copper Country of the state of Michigan in the United States. The mine is at the now-abandoned town of Clifton in Keweenaw County. Mining began in 1845, and the Cliff was the most productive copper mine in the United States from 1845 through 1854. Large-scale mining stopped in 1878.

<span class="mw-page-title-main">Calumet Historic District</span> Historic district in Michigan, United States

The Calumet Historic District is a National Historic Landmark District that encompasses most of the village of Calumet, Michigan. The district was designated in 1989 for the community's importance in the history of the region's copper mining industry.

The Osceola Mine was a copper mine consisting of 11 shafts located in Osceola Township, Houghton County, Michigan. In 1895, it was the site of the deadliest mine disaster in the Copper Country.

The Victoria Mine is the name given to a series of copper mines located in Rockland Township, Ontonagon County, in Michigan's Copper Country. It was near this location that a large piece of float copper, known as the Ontonagon Boulder, was found. The mine operated off and on from 1849 until its final closure in 1921. Most of the metal found there was low grade native copper from the Forest Lode. Quartz, epidote, calcite, prehnite, and pumpellyite are also found in the rock.

References

  1. 1 2 3 4 5 White, Walter S. (1968). "The Native-Copper Deposits of Northern Michigan". Ore Deposits of the United States, 1933–1967. Vol. 1. New York: American Institute of Mining Engineers. pp. 303–325.
  2. "Halfbreed: Halfbreed mineral information and data". Mindat.org. Hudson Institute of Mineralogy.
  3. Cleland, Charles E. (1992). Rites of Conquest: The History and Culture of Michigan's Native Americans. Ann Arbor: University of Michigan Press. p. 18. ISBN   0472064479 via Google Books.
  4. Martin, Susan R. (1995). "The State of Our Knowledge About Ancient Copper Mining in Michigan". The Michigan Archaeologist. 41 (2–3): 119–138. Archived from the original on February 7, 2016. Retrieved August 31, 2017.
  5. Mulholland, James A. (1981). A History of Metals in Colonial America. University: University of Alabama Press. pp. 41–42.
  6. 1 2 Lankton, Larry (2010). Hollowed Ground. Detroit: Wayne State University Press. pp. 13–14. ISBN   9780814334904.
  7. Crane, W.R. (1929). Mining Methods and Practice in the Michigan Copper Mines. United States Bureau of Mines. p. 3. Bulletin 306.
  8. Stevens, Horace J. (1909). The Copper Handbook. Vol. 8. Houghton, MI: Horace Stevens. p. 1466.
  9. Courter, Ellis W. (1992). Michigan's Copper Country. Lansing: Michigan Department of Environmental Quality. pp. 136–137.
  10. Thurner, Arthur W. (1994). Strangers and Sojurners: A History of Michigan's Keweenaw Peninsula. Detroit: Wayne State University Press. p. 286.
  11. Bornhorst, Theodore J.; Paces, James B.; Grant, Norman K.; Obradovich, John D.; Huber, N. King (May 1988). "Age of Native Copper Mineralization, Keweenaw Peninsula, Michigan". Economic Geology. 83 (3): 619–625. doi:10.2113/gsecongeo.83.3.619.
  12. Binder, David (September 14, 1995). "Upper Peninsula Journal; Yes, They're Yoopers, and Proud of It". The New York Times.
  13. Silfven, Ken; Johnson, Robin (May 28, 1996). "DEQ Press Release" (Press release). Archived from the original on September 29, 2007. Retrieved August 6, 2007.
  14. "Environmental Justice Case Study: Solution Mining in White Pine, MI and the Bad River Reservation". SNRE 492 Course Section of the Environmental Justice Institute. University of Michigan School of Natural Resources and Environment.
  15. Williams, Tom (August 2004). "White Pine Mine". Ecosystem Restoration. Archived from the original on December 12, 2012. Retrieved August 28, 2007.
  16. Egan, Paul (April 22, 2012). "Company Wants to Grow Quality Medical Marijuana in Old Mine". Detroit Free Press . Retrieved April 24, 2012.
  17. "Mining set to return to White Pine". keweenawreport.com. Keweenaw Report. July 7, 2021. Retrieved July 9, 2021.
  18. "Eagle". Lundin Mining Corporation. Retrieved May 15, 2019.
  19. Casey, Steve; Wurfel, Brad (March 19, 2013). "Permit Signed for Copperwood Mine Project" (Press release). Michigan Department of Environmental Quality. 13-319. Archived from the original on April 3, 2013.
  20. Keane, Joseph M.; Milne, Steve; Kerr, Thomas (March 21, 2012). Feasibility Study of the Copperwood Project, Upper Peninsula, Michigan, USA (PDF). Tucson, AZ: K D Engineering. Q431-01-028. Archived from the original (PDF) on December 3, 2013. Retrieved November 17, 2013.

Further reading