Uranium mining around Bancroft, Ontario, was conducted at four sites, beginning in the early 1950s and concluding by 1982. Bancroft was one of two major uranium-producing areas in Ontario, and one of seven in Canada, all located along the edge of the Canadian Shield. In the context of mining, the "Bancroft area" includes Haliburton, Hastings, and Renfrew counties, and all areas between Minden and Lake Clear. Activity in the mid-1950s was described by engineer A. S. Bayne in a 1977 report as the "greatest uranium prospecting rush in the world".
As a result of activities at its four major uranium mines, Bancroft experienced rapid population and economic growth throughout the 1950s. By 1958, Canada had become one of the world's leading producers of uranium; the $274 million of uranium exports that year represented Canada's most significant mineral export. By 1963, the federal government had purchased more than $1.5 billion of uranium from Canadian producers, but soon thereafter the global supply uranium market collapsed and the government stopped issuing contracts to buy. Mining resumed when uranium prices rose during the 1970s energy crisis, but this second period of activity ended by 1982.
Three of the uranium mines are decommissioned, and one is undergoing rehabilitation. A twofold increase in lung cancer development and mortality has been observed among former mine workers. Bancroft continues to be known for gems and mineralogy.
Geology and mineralogy During the most recent ice age, in the area of what is now Bancroft, Ontario, ancient glaciers removed soil and rock, exposing the Precambrian granite that had been the heart of volcanic mountains on an ancient sea bed. During the Grenville orogenies, sedimentary rocks were transformed by heat and pressure into banded gneiss and marble, incorporating gabbro and diorite (rich in iron and other dark minerals). Some uranium ores in these structures are about 1,000 million years old, while others are understood to be 1,200 million years old.
In Canada, 99% of known uranium occurrences and 93% of properties producing uranium are located on the geological shield known as the Canadian Shield, almost all on the western and southern edges of it. The Grenville Province in Eastern Canada has small quantities of uranium-thorium-rare earth element in granitic pegmatite which appear in numerous locations around the Bancroft area, giving Bancroft the moniker of the "Mineral Capital of Canada". The "Bancroft area" includes Haliburton, Hastings, and Renfrew counties, and all areas between Minden and Lake Clear.
Bancroft is unusual as one of the limited global locations where uranium is extracted from intrusive rocks, notably the only one from the pegmatite type. Other locations include the Rössing and Husab mines in Namibia, Kvanefjeld in Greenland, Palabora in South Africa, along with the Radium Hill mine and sites in Southern Australia's Olary Province. The key geological features in the Bancroft area relevant to uranium mining are three circular granitic complexes, each about across. They are (from southwest to northeast):
The Cheddar complex is a circular double dome of granitic rock surrounded by paragneiss, para-amphibolite, and pyroxene granulite. All these rocks contain younger granitic and syenitic intrusions. The Cardiff plutonic complex consists mainly of three southeast-dipping cylindrical sheet intrusions: the Centre Lake granite, the Monck Lake granite, and the Deer Lake syenite. They intrude metasedimentary rocks. The Faraday granite is a sheet of granite covered by gneisses and metagabbro. The Faraday granite sheet dips to the south and it is the southern edge of the Hastings Highland gneiss complex.
Gems and other resources
Finds of gold in nearby Madoc, Ontario, (then known as Eldorado) from 1886 to 1887, inspired many to seek gold around Bancroft. Surface gold was found in October 1897 by R. Bradshaw, southwest of Bancroft (towards Bobcaygeon). This triggered a rush of prospectors to the area. Iron and magnetic ores were mined from 1882, gold, copper and mica from the late 1890s, and marble from 1911. More than 1,600 identifiable minerals and non-metallic collectibles can be found in the area, including 175 species of gemstones.
Aside from uranium, mines in the Bancroft area produced sought-after gemstones of 175 species, most notably calcite, clinohumite, corundum, diopside, dravite, edenite, euxenite-(Y), ferri-fluoro-katophorite, fluorapatite, fluorite, fluoro-richterite, ilmenite, kainosite-(Y), molybdenite, nepheline, phlogopite, crystals of the pyrochlore supergroup, thorite, titanite, tremolite, uraninite, uranophane, and zircon. Madawaska Mine produced samples of the very rare kainosite-(Y), globally renowned samples of the common calcite and fluorite, "superb" samples of ilmenite, and "fine" samples of molybdenite. +Resources (other than uranium and gems) extracted in the Bancroft areaFromResourceLocations mined1882IronCoe Hill, Mayo (now Carlow/Mayo), Egan Creek (now Bancroft)1882Magnetic ore, arsenical pyrites and quartzBradshaw1897 GoldBancroft1898CorundumCarlow, Raglan1899CopperDungannon, Cardiff, Maynooth1899MicaCardiff, Paudash Lake1905SodalitePrincess Sodalite Mine, near Bancroft1911MarbleFaraday, Dungannon Marble mined in Bancroft was used to make the floor of the Whitney Block and the Royal Ontario Museum.
Uranium mining Uranium was first discovered in the area of Cardiff, Ontario, in 1922 by prospector W. M. Richardson. His find was first called "the Richardson deposit" and later "the Fission property" and is located east of the Wilberforce community of Cardiff township. Between 1929 and 1931, attempts were made to extract radon from the uranium ore dug from a tunnel driven into a hill.
In 1943, during World War II, global interest in mining uranium escalated. The government sent geologists to Bancroft, who concluded that all known uranium deposits were unviable due to accessibility, size and uranium concentration. 1948 saw an increase in private staking of claims for uranium, but due to the difficulties in extracting uranium from lower grade ore, none developed into mines.
In 1953, "intelligent prospecting and excellent preliminary exploration" by G. W. Burns, R. J. Steele and Arthur H. Shore led successful prospecting of the area. Between 1953 and 1956, 100 claims were staked around Bancroft and at approximately the same time, another ten mines were started in the Elliot Lake area. Burns and Steele discovered the Central Lake deposits, which were developed into Bicroft Mine, while Shore's prospect became the Faraday Mine.Activity in the mid-1950s was described by engineer A. S. Bayne in a 1977 report as the "greatest uranium prospecting rush in the world".
Uranium mining operations in the Bancroft area were conducted at four sites, beginning in the early 1950s and concluding by 1982. Each of these used underground hard-rock mining methods to access and collect uranium ores from the surrounding granite and gneiss. The mines were: +Major uranium mines in the Bancroft areaMine (years active)Geological featureOre milledUranium oxide producedFaraday Mine Faraday GraniteMadawaska Mine (1976–1982)Bicroft Mine (1957–1963)Cardiff Complex1957–1960: 49,904 kg (133,693 lb)1961–1962: 127,659 kg (342,000 lb)1962–1963: 430,000 kg (950,000 lb)Dyno Mine (1958–1960)Cheddar GraniteGreyhawk Mine (1957–1959, 1976–1982)Faraday Granite1957–1959:
Bicroft Mine
In 1952 G. W. Burns, an amateur prospector from Peterborough, found uranium deposits 16 kilometres (10 mi) southwest of Bancroft, near Cardiff township and Paudash Lake. At another property near Centre Lake (between Cheddar and Cardiff), he observed purple rocks which he knew to be fluorspar, an indicator of radioactive geology. He brought the samples to Robert Steele in Peterborough who used a Geiger counter to confirm their radioactivity. The two then formed a partnership and immediately began staking land claims. Their slow careful staking disadvantaged them as others rushed to the area and staked their own claims; nonetheless, their work paid off and they started mining what the Geological Survey of Canada (GCS) confirmed to be uraninite.
In late 1952, Burns sold his property to a Toronto syndicate that formed into the Centre Lake Uranium Mines Limited, led by C. C. Huston. The company worked on the surface, opened an adit and started diamond drilling, mostly every , sometimes between the holes. A shaft was created in 1954. Simultaneous to this, Croft Uranium Mines Limited, a subsidiary of Macassa Mines Limited, formed in 1953 and discovered uranium north of the original site. In 1955 the two sites were merged under the ownership of Bicroft Uranium Mines Limited, with work focused on the Centre Lake part of the property. A shaft was sunk to and ten levels created. A treatment plant capable of processing of ore per day was built and operations started in late 1956. Production in 1957 was of U3O8 from ore with a grade of 0.0859%. Production increased to per day in 1958 and exploration started to the south of the site. Mining continued until 1963, producing about of uranium ore.
of tailings remain on site in two impoundments. Repairs to the decommissioned site, including the addition of vegetation over the tailings, were completed in 1980. Subsequent upgrades of the dams were completed in the 1990s. The site is now a wetlands.
The uranium deposits of Bicroft mine occur in a set of eastward-dipping en-echelon lens-shaped dykes of syenite and granite, up to wide and long, which extend over an area of about within a north–south oriented belt of amphibolite and paragneiss (the eastern part of the Centre Lake granite). The ore minerals are uranothorite and uraninite. The uranium-to-thorium ratio is variable. Pyroxene-rich granite of this area is richer in thorium.
Faraday Mine/Madawaska Mine
The area that is now known as Madawaska Mine was first mapped by Jack Satterly in the early 1950s.
Arthur H. Shore, an independent prospector, first found uranium at his lot on Faraday township in 1949. He founded Faraday Uranium Mines Limited in 1949, but injured himself shortly afterwards. Newkirk Mining Corporation led work in 1952, including diamond drilling in December 1952 which helped identify seven main zones of uranium ore. Further drilling the following year identified additional deposits to a depth of . 1954 drilling found more uranium and adits were created. By 1955 it was established that there were of ore that was 0.112% U3O8 (uranium oxide). A sale price was agreed in January 1956. A shaft was sunk from an adit, from which five levels were established. A treatment plant with a capacity was built and operations started in April 1957. In 1958, the treatment capacity was increased to per day in order to support processing of ore from Greyhawk Mine. Production in 1957 was from ore with a grade of 0.0859% U3O8. Between 1948 and 1964 Faraday Mine had produced $54 million of ore.
After $7 million of investment to rehabilitate the mine, it reopened as the Madawaska Mine in 1976 and production continued to 1982. The shaft into the uranium-bearing pegmatite reached a depth of . During this period, the mine was producing of ore per day.
In 2015, inspections found improper surface protection of the tailings and the site has been undergoing rehabilitation.
At the Faraday and Madawaska mines, lens-shaped bodies of ore occur in granitic pegmatite dykes within an area of steeply-dipping amphibolite and metagabbro at the southern edge of the Faraday granite. Uraninite and uranothorite are the principal ore minerals at Faraday and Madawaska. Other radioactive minerals found at this locality include allanite, cyrtolite (a uranium-thorium rich variety of zircon), uranophane-α and uranophane-β. The uranium-to-thorium ratio is about 2-to-1. Uranium ore concentrations range from 0.07 to 0.4 per cent U3O8 (uranium-oxide.)
Dyno Mine