In Michigan, copper mining became an important industry during the 19th and early 20th centuries. This growth began the development of copper mining as a major industry in the United States.

Geology

Copper is found mainly in the western part of the Upper Peninsula in Michigan, in an area called the Copper Country. This area is unique because copper is mostly found as pure copper metal, known as native copper, rather than in forms like copper oxides or copper sulfides found in other mining areas. The copper deposits are located in very old rocks from the Precambrian period, which include thick layers of sandstone, conglomerate, ash beds, and flood basalts linked to the Keweenawan Rift.

Native copper is found in cracks, steep veins, or in the amygdaloid top layer of the Portage Lake Lava Series, which includes lava flows and conglomerate beds. This lava series is at least 15,000 feet thick in the Michigan copper district and consists of hundreds of flood basalt layers. The rocks in this area are from the Precambrian period and belong to the Keweenawan Series. Mining in the region began by extracting copper from fissures, later shifting to amygdaloidal deposits.

Although native copper was the main type of copper found, chalcocite (a copper sulfide) was sometimes present. In the Mohawk mine, copper arsenide minerals like mohawkite and domeykite were also found. Other minerals, called gangue minerals, included calcite, quartz, epidote, chlorite, and various zeolites. Some copper mines also contained significant amounts of silver, which appeared either as pure silver or mixed with copper. A special term, "halfbreed," describes an ore sample containing both pure copper and pure silver in the same piece of rock. This type of ore is only found in the native copper deposits of Michigan’s Upper Peninsula.

Native American

Native Americans were the first people to mine and use copper from Lake Superior and the Keweenaw Peninsula in northern Michigan between 5000 BCE and 1200 BCE. They made tools from this copper. Archaeologists have found evidence of copper mining, such as pits and hammering stones, in the Keweenaw Peninsula and Isle Royale. Some sources say that up to 1.5 billion pounds of copper may have been mined during this time, but other archaeologists believe these numbers are not accurate and that the real amount is unknown. Archaeologist Susan Martin wrote that studies of ancient sites in the Lake Superior area show that copper was used continuously throughout the prehistoric period. These sites were dated using radiocarbon methods, and copper was still being worked until Europeans arrived in the 17th century.

By the time European explorers reached the region, the Ojibwe people lived there. They did not mine copper themselves. According to Ojibwe traditions, they replaced the earlier people who had mined copper. The first written record of copper in Michigan was made by French missionary Claude Allouez in 1667. He noted that Native Americans in the Lake Superior area valued copper nuggets they found. Native Americans guided missionary Claude Dablon to the Ontonagon Boulder, a large piece of copper weighing 1.5 tons along the Ontonagon River. When American prospectors arrived in the 1840s, they found copper pieces in streams and on the ground.

Douglass Houghton’s 1841 report about copper, the Treaty of La Pointe in 1843, the spread of news about the Ontonagon Boulder, and the opening of a federal mineral land office in Copper Harbor led to a rush of miners. The abandoned copper pits left by Native Americans helped early miners find many of the first successful mines. All the major copper deposits were discovered before 1900, and each was found in areas close to the ground.

Modern mining industry

In 1841, the Michigan State Geologist Douglass Houghton (who later became mayor of Detroit) reported on copper deposits, which led to a rush of people searching for copper. Mining occurred along a long strip of land about 100 miles long, stretching through Ontonagon, Houghton, and Keweenaw counties. Isle Royale, located on the north side of Lake Superior, was explored and a smelter was built, but no major mining took place there. Some copper was found in Keweenawan rocks in Douglas County, Wisconsin, but no successful mines were developed there.

Copper mining in the Upper Peninsula grew quickly, and from 1845 until 1887 (when it was surpassed by Butte, Montana), the Michigan Copper Country was the nation’s top copper producer. Between 1850 and 1881, Michigan produced more than three-quarters of the country’s copper each year, and in 1869, it produced over 95% of the nation’s copper.

Commercial copper mining began in 1844 at the Phoenix mine. Early miners often lacked knowledge and planning, and few mines produced copper or made money. The first successful copper mine, the Cliff mine, started operations in 1845, followed by many others. These early mines worked copper-filled cracks in the rock that crossed layers of stone.

Although the copper-mining region stretched about 100 miles from northeast to southwest, the most productive early mines were 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 cracks in the rock were nearly vertical and ran perpendicular to the surrounding basalt and conglomerate layers. In Ontonagon County, the cracks ran nearly parallel to the surrounding layers and tilted slightly downward.

Miners sometimes found large masses of pure copper weighing hundreds of tons. Extracting these masses required months of chiseling them into smaller pieces to remove from the mine. Although the copper was pure, removing it was difficult and often not profitable. Most copper recovered was "barrel copper" (pieces broken from the rock and sorted manually in a "rock house" before being shipped in barrels) or finer copper broken loose in stamp mills and separated by gravity in "buddles" or "jigs."

In the 1850s, mining began on copper deposits in felsite-pebble conglomerates and upper layers of basalt lava flows (called amygdaloids). These deposits were lower quality than the cracks but much larger and easier to mine. Ore was blasted out, hoisted to the surface, and sent to stamp mills elsewhere. Amygdaloid and conglomerate mining became more productive and profitable than mining cracks, and most successful mines were on these deposits. The first mine to successfully mine a stratiform deposit 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."

While the most successful crack-based mines were at the north and south ends of the region, the conglomerate and amygdaloid mines, which produced most of Michigan’s copper, were concentrated in the center of the region, mostly in Houghton County. These mines were located along a strip about two miles wide and 24 miles long, stretching from the Champion mine on the southwest to the Ahmeek mine on the northeast, passing through Houghton, Hancock, and Calumet.

In the early 20th century, copper companies began to combine operations. Most mines in the Copper Country were controlled by two companies: the Calumet and Hecla Mining Company north of Portage Lake and the Copper Range Company south of Portage Lake.

Annual copper production peaked in 1916 at 266 million pounds (121,000 metric tons). Most mines closed during the Great Depression due to low copper prices. Many reopened during World War II when demand for copper increased. After the war, prices dropped, and nearly all companies closed, leaving only Calumet and Hecla, Quincy, and Copper Range. These companies survived by reprocessing leftover waste from older mining operations to extract copper.

By 1968, Calumet and Hecla was bought by Universal Oil and became its Calumet division. By then, its original mines had been abandoned, and reclamation of waste had ended. The company could not produce enough copper to meet its needs. It drilled new shafts and reactivated old ones but found no success. That year, workers went on strike, and the new owners closed the mines permanently. Only the Copper Range Company’s White Pine mine remained open, and its ore was mostly copper sulfides, not native copper. Michigan’s native copper industry had ended after producing 11 billion pounds (5.0 million metric tons) of copper.

Several companies tried to reopen mines in the next two decades, including Homestake Mining Company, but none lasted more than a few years or were profitable.

For over 100 years, copper mining was the main source of income in the Copper Country. The town of Red Jacket (now Calumet) used its budget surplus to build The Calumet Theatre, an opulent opera house that hosted famous plays and performers. Wealthy mine managers built mansions that still line the streets of former mining towns. Towns like Calumet, Houghton, Hancock, and Ontonagon existed mainly because of copper mining. As mines closed, the region lost its economic base, and population dropped sharply. Many small towns became ghost towns

White Pine mine

The copper-rich Nonesuch Shale in Ontonagon County, Michigan, was known since the 1800s. However, the copper content was too low, the copper particles were too small, and most of the copper was found in sulfides rather than as native copper. These conditions made the shale deposits difficult to mine profitably, even though mining attempts were made at the Nonesuch Mine.

In 1955, the Copper Range Company began large-scale mining at the White Pine Mine, located near the old Nonesuch Mine. The deposit is a layered rock formation found in the lower 15 meters of the Proterozoic Nonesuch Shale and the upper 2 meters of the Copper Harbor Conglomerate. The main ore mineral was chalcocite, though native copper was more common in the lower layers. The mine was very successful, producing over 1.8 million metric tons (4.0 billion pounds) of copper during its operation. The White Pine Mine, the last major copper mine in Michigan, closed in 1995.

The company requested permission to continue mining using in-situ leaching, a method that uses sulfuric acid to extract copper from the ground. The Michigan Department of Environmental Quality approved the permit in May 1996, and the company started a pilot project. However, members of the Bad River Indian Reservation in Wisconsin blocked rail shipments of sulfuric acid to the mine, forcing the company to transport acid by truck. The U.S. Environmental Protection Agency (EPA) later stated that the company needed a federal permit for the project. In October 1996, the company paused the in-situ leaching process and applied to the EPA for a permit. In May 1997, the company withdrew its permit application, citing delays that made the project unprofitable, and announced plans to reclaim the mine site.

The waste storage area at the White Pine Mine is currently experiencing significant environmental damage. From 1997 to 1999, the University of Montana worked to restore and plant vegetation on the barren land, but it is unclear if the efforts were successful. The university published a detailed report on its work. Satellite images of the area are available at coordinates (46°47′17.91″N 89°31′47.97″W).

In 2012, a company called SubTerra used the mine for pharmaceutical research.

The July 7th, 2021, edition of the local news outlet Keweenaw Report included the headline: "Mining set to return to White Pine."

Eagle Mine

Eagle Mine is a rich deposit of nickel and copper found in the Upper Peninsula of Michigan. It is located on the Yellow Dog Plains, about 25 miles northwest of Marquette. Rio Tinto discovered the mine in 2002, and Lundin Mining later purchased it in 2013. Construction began in 2010, and the mine started producing minerals in 2014. Mining is expected to continue for nine years, ending in the fourth quarter of 2023. After mining stops, the site will be restored. Over its nine-year operation, the mine is expected to produce 360 million pounds of nickel, 295 million pounds of copper, and small amounts of other metals, including platinum, palladium, and cobalt. Ore from the mine will be processed at the Humboldt Mill in Michigamme Township. The processed material will be sent by train to smelters in Canada or Europe. Eagle Mine was the first project approved under Michigan's Non-Ferrous Metallic Mining Law, also called Part 632.

Copperwood Mine

On March 13, 2013, the Michigan Department of Environmental Quality (DEQ) gave final permits to Orvana Corporation, based in Toronto, Ontario, to begin mining north of Wakefield in Gogebic County.

Orvana estimates that about one billion pounds of copper are present at their site, along with smaller amounts of silver. Studies suggest that 800 million pounds (360,000 metric tons) of copper can be removed, as well as 3,456,000 ounces of silver. Production would last 13 years based on these reserves. In 2014, the project was purchased by Highland Copper Company, a Montreal-based exploration company. An updated feasibility report is currently being prepared, and permits for the project are expected to be completed by the end of 2018.

Back Forty Mine

The Back Forty Mine is a proposed open-pit mine that would extract gold and zinc deposits located in Menominee County, in the South Central part of the Upper Peninsula of Michigan, near the Menominee River.