In 1948, prospecting duo Aimé Breton and Carl Gunterman came across a rock at the Sault Ste. Marie recording office, labelled only "Long Township," which sent their geiger counters clicking. The two set out to find the source of the radioactive rock, but this township represented 36 square miles of heavily wooded country. Not deterred, Breton and Gunterman eventually tracked down the mystery rock, staked the area, and started looking for a buyer. 

This proved difficult because although geiger counters indicate a strong presence of radioactive materials, all surface samples revealed only very trace amounts. Time lapsed without anything worthwhile being found, and with it, so too did the claims.

One prospector-geologist who refused to let this paradox rest was Franc Joubin. Backed financially by Joseph Hirshhorn, Joubin pursued his theory at the risk of a $30,000 diamond-drilling program, which confirmed his wildest hopes: while the uranium values in the rock surface had been leached out and lost during centuries of exposure, below the surface they were very much intact.

Despite the 36 claims (1440 acres) staked around their successful drilling operation, the Hirshhorn-Joubin team set their sights on prospecting the entire 129 kilometres of "The Big Z" wherever there seemed to be any prospect of mineral.

  

(left: W.H. Collins geological map published in 1925; right: the "Z" form can be viewed in the lower right, slicing through the pink)

"The Big Z" refers W.H. Collins map, published through the Geological Survey of Canada in 1925, which shows a distinct break between old rocks and an area of younger sedimentary deposits. The contact between these rock formations runs north-westerly from the shore of Lake Huron, tracing roughly 129 kilometres through 14 townships, and appears in the form of a "Z."

The Hirshhorn-Joubin uranium discovery lay in a layer, or "reef," at the bottom of the younger rocks, and it was their belief that mineralization would continue to occur along most of the length of the contact.

Secrecy was vital to the success of this operation. By June 1, 1953, enough men were found and miners' licenses were obtained from enough different mining recorders' offices throughout the province to thoroughly conceal their intent. With everything prepared, they set out on the campaign that was to be known as "The Backdoor Staking Bee."

Planeload after planeload carried a dozen geologists, mining engineers, and 80 prospectors into the wilderness. Several young lawyers were also in accompaniment to ensure that each man's claim transfers and application to record claims were completed correctly. The planes took off from Timmins and other northern centres at irregular intervals. No one paid much attention to the plane traffic, assuming these carried timber cruisers or sportsmen.

By July 9, 1953, the job was done and the group moved out of the bush to converge on the recorders' offices, where they filed more than 1400 claims covering 56,000 acres.

The secret had been kept, but once the news broke about these new claims, a major rush started and invading prospectors staked an additional 8000 claims in the most promising parts of the areas which were still open. All of this activity was compressed into a period of a few weeks—a taste of what was to follow.

Scores of diamond-drilling rigs and their crews were flown into the area. With hundreds of holes and intense scrutiny, it was determined that the largest deposits of uranium were found in the middle and north arms of "The Big Z" formation.

At the site of the original discovery, Pronto Mine was established with a mill designed to process 1500 tons of ore daily. Nearly every time-record known to the mining industry was shattered in getting Pronto's mill wheels turning, opening for business October 15, 1955.

Farther north, the pace of activity could be described only as frantic, as plans were implemented to establish eleven separate mines, ten of them to be completed with mill installations, within a few kilometres of the middle and north arms of "The Big Z." The smallest of these individual operations would  dwarf most other uranium mining enterprises in the world, with the exception of South Africa, where uranium is produced as a by-product of their gold mines.

Once the immensity of the ore reserves was known, the Canadian Government negotiated contracts with the Atomic Energy Commission of the United States to a total of more than 1500 million dollars worth of uranium oxide. Of this, more than one billion tons was to be supplied by the Elliot Lake Mines, to be delivered by 1963. This meant that the mines had to be brought into production with great speed. Within a few years, Elliot Lake's thirteen uranium mines—Quirke, Denison, Panel, Can-Met, Stanrock, Spanish-American, Stanleigh, Milliken, Lacnor, Nordic, Pronto, Buckles, and Pater—were fully operational.

On November 6, 1959, the Canadian government announced that it had been unable to get the Atomic Energy Commission in Washington to extend its contracts beyond 1962. The United States stated that they had sufficient domestic sources to fulfill the expected requirements, although the existing contracts with the Canadian producers would be fulfilled.

Matters worsened when Rio Algom announced that four of their six Elliot Lake mines would close within the year of 1960, and the two remaining would stay in production until 1966.

In response to the impending closure of the mines, citizens in Elliot Lake raised protest to the government, but to no avail. The population dropped from 25,000 to 5000 people.

By the mid 1970s there was another boom in Uranium production and Elliot Lake was given a second chance. Despite this resurgence, Elliot Lake never reached the population growth it saw at the peak of mining.

In September 1990, the layoffs began once again. Denison Mines officially closed their doors in May 1992 and the last remaining mine, Rio Algom's Stanleigh, would close in June 1996. 

If not for the Elliot Lake Miners' Memorial Park, you would be hard-pressed to find evidence of the City's mining heritage. The mine decommissioning completed by Rio Algom Ltd. and Denison Mines Inc. is world-class, and any remaining traces of mining operations are being restored back to nature.

These old sites now pose no risk to the public; all of the sites have now been substantially decommissioned, with all mine features capped or blocked, all facility structures demolished, and all sites landscaped and revegetated (active decommissioning).

The effectiveness of site remediation and the influence on the surrounding environment are being monitored.

The Serpent River Watershed Monitoring Program is an extensive program that monitors the environmental quality across the basin and near the Pronto site, which is located outside of the watershed.

The program was designed in consultation with federal and provincial regulators, including the Canadian Nuclear Safety Commission (CNSC). Assessments of monitoring results have been presented in periodic environment reports.

Rio Algom Limited and Denison Mines Limited are licensed by the CNSC to operate historical mine sites in Elliot Lake, Ontario. The results of the Independent Environmental Monitoring Program (IEMP) for 2015 and 2018 confirm that the public and the environment around the Elliot Lake historical mine sites are protected and that there are no expected health or environmental impacts.

The Quirke Mine site is located 16km north of Elliot Lake. Quirke was part of Algom Uranium Mines Ltd, a wholly-owned subsidiary of the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto Group of mines amalgamated to form Rio Algom Mines Ltd.

Quirke has two shafts and the properties were known as Quirke I and Quirke II. From 1957 to 1960, about 3.7 million tons of ore were produced at Quirke I. When the mine reopened in 1967, the mill was expanded from 3000 tons per day to 4700 tons per day and the shaft for Quirke II was completed. During the next 13 years, the mine produced another 42 million tons of ore.

The Denison Mine and Mill commenced production in May of 1957, with a capacity of 500 tons per day. Its production capacity was gradually increased to 13,600 tons per day by the early 1980s. The mine ceased its operations in April of 1992.

The Panel Mine site is located on the north shore of Quirke Lake approximately 23km northeast of Elliot Lake. In 1956, Panel became part of Northspan Uranium Mines Ltd, a wholly-owned subsidiary of the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto Group of Mines amalgamated to form Rio Algom Mines Ltd.

Panel operated from December 1957 to June 1961 with a milling capacity of 3000 tons per day and produced about 3.5 million tons of ore. The mine re-opened in 1979 with a milling capacity of 3000 tons per day and produced 12.5 million tons of ore before it shut down permanently in August 1990.

The Can-Met Mine and Mill began production in October of 1957, with a design capacity of 2700 tons per day. In March of 1960, Can-Met Explorations Ltd. amalgamated with Consolidated Denison Mines Ltd. Operations at the Can-Met Mine were suspended shortly thereafter.

The Stanrock Mine and Mill commenced production in March of 1958 with a design capacity of 2700 tons per day. The mine closed in October of 1964. From 1964 to 1970, uranium was recovered in the Stanrock Mill from mine water enriched by underground bacterial leaching. Mine-water pumping, and lime treatment on the surface, resumed in 1979 and continued until the mid-1990s.

Spanish American Mine site is located on the south shore of Quirke Lake about 15km northeast of Elliot Lake. In 1956, Spanish American became part of Northspan Uranium Mines Ltd, a wholly-owned subsidiary of the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto Group of mines amalgamated to form Rio Algom Mines Ltd.

Spanish American operated from March 1958 to February 1959 with a milling capacity of 2000 tons per day and produced approximately 400,000 tons of ore. The Mine closed prematurely since the contract requirements could be produced by the two other Northspan properties, Lacnor and Panel mines.

The Stanleigh Mine site is located 2km northeast of Elliot Lake. In June 1960, Stanleigh Uranium Mining Corporation was acquired by Preston Dome East Mines, which was controlled by the Rio Tinto Mining Company Ltd. In August 1960, Stanleigh and Preston amalgamated under the name of Preston Mines Ltd.

Stanleigh operated from December 1957 to November 1960 with a milling capacity of 3000 tons per day and produced about 2.3 million tons of ore. In 1978, Preston Mines signed a long-term contract with the Ontario Hydro for the delivery of 72 million pounds of uranium oxide from 1984 to 2020. The mine closed prematurely in June 1996 when Ontario Hydro cancelled its contract with Rio Algom Ltd. Stanleigh produced approximately 13 million pounds of ore from 1983 to 1996.

The Milliken Mine site is located less than 3km northeast of Elliot Lake. The Rio Tinto Mining Company of Canada Ltd acquired Milliken in 1956. In June 1960, the Rio Tinto Group of mines amalgamated to form Rio Tinto Algom Mines Ltd.

Milliken operated from March 1958 to September 1965 with a milling capacity of 3200 tons per day. Although mining operations ceased in June 1964, underground bacterial leaching continued on an experimental basis for another year. Throughout its operations, Milliken produced about 6.3 million tons of ore.

Lacnor Mine, which was originally called Lake Nordic Mine, was located approximately 5km northeast of Elliot Lake. In 1956, Lacnor became part of Northspan Uranium Mines Ltd, a wholly-owned subsidiary of the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto Group of Mines amalgamated to form Rio Algom Mines Ltd.

Lacnor operated from September 1957 to July 1960 with a milling capacity of 4000 tons per day and produced approximately 3.3 million tons of ore.

The Nordic Mine site is located about 8km southeast of Elliot Lake. Nordic was part of Algom Uranium Mines Ltd, a wholly-owned subsidiary of the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto group of mines amalgamated to form Rio Algom Mines Ltd.

Nordic operated from November 1956 to September 1970 with a milling capacity of 300 tons per day and produced approximately 13 million tons of ore. Mining operations ceased in July 1968, but bacterial leaching, training, and experimental mining continued to be carried out until 1970. The uranium oxide packing plant remained in operation until Quirke and Panel mines shutdown in August 1990.

The Pronto Mine site is located about 20km east of Blind River. In 1953, geologist Franc Joubin convinced American financier Joseph Hirshhorn to provide $35,000 to cover the drilling expenses on a property where surface rock samples indicated radioactive ore but assay results were always disappointing. The drill core results revealed a large ore body and the Algoma region soon became the world's largest uranium find. In 1956, Hirshhorn's interests were acquired by the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto group of mines amalgamated to form Rio Algom Mines Ltd.

Pronto operated from October 1955 to April 1960 with a milling capacity of 1500 tons per day and produced about 2.3 million tons of ore. In 1960, the mill was converted to process copper ore from nearby Pater Mine until 1970. 

Buckles Algoma Uranium Mines Ltd, located about 4km south of Elliot Lake, was named after Harry Buckles, the field manager who worked for Joseph Hirshhorn and was involved in the staking operations of the Big Z uranium discovery in the area. In 1956, Buckles became part of Northspan Uranium Mines Ltd, a wholly-owned subsidiary of the Rio Tinto Mining Company of Canada Ltd. In June 1960, the Rio Tinto Group of mines amalgamated to form Rio Algom Mines Ltd.

Buckles operated from December 1956 to October 1958 when all available high-grade ore was mined out. Approximately 276,000 tons of ore were transported to Spanish American and Lacnor mills for processing. The shallow mine with a shaft depth of only 239 feet operated around the clock, seven days a week.