Uranium mining in the Bancroft area

Hewitt described the Cheddar complex as:

"a circular double dome of granitic rock, six miles (10 km) in diameter, mantled by limy paragneiss, para-amphibolite, and pyroxene granulite all of which are intruded and partly replaced by syenitic and granitic rocks."[5]

Located north of Cheddar granite, the Cardiff complex was described by Hewitt as:

"the shape of a cylinder plunging to the southeast and consists of three main intrusive sheets: the Centre Lake granite, the Monck Lake granite, and the Deer Lake syenite. It also is flanked by metasediments intruded and replaced by syenitic and granitic rocks; much sedimentary material occurs in wide bands within the plutonic complex."[5]

Located east of the others, the Faraday complex, as described by Hewitt, is a:

"south-dipping granite sheet forming the south margin of the Hastings Highland gneiss complex. It is overlain by a zone of mixed hybrid gneisses including metasediments, granitic and syenite rocks and metagabbro. The three intrusive complexes and their flanking metasediments show more or less concentric trend-lines."[5]

Aside from uranium, Bancroft area and its' mines produce sought-after gem stones 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 flourite, "superb" samples of ilmenite, "fine" samples of molybdenite, and the best known samples of molybdenite.[3]

Surface gold was found in October 1897 by R. Bradshaw between Bobcaygeon and Bancroft (20 miles from Bancroft), triggering a rush of prospectors to the area who discovered the following resources:[1]

In 1952 G. W. Burns, a well studied amateur prospector from Peterborough found deposits near Cardiff township, 10 miles southwest of Bancroft, near Paudash Lake. In an 18 Dec 1955 letter to the Geographical Survey of Canada, Mr Burns stated:[5]

"I always was interested in rock and minerals but did not know very much about what I was looking at and purchased a piece of property in Cardiff Twp. on which was a nice large showing of what I was told was molybdenite but after purchasing property found out it was only large flake graphite (and by the way I still hold this so called molybdenite deposit). This was in 1948 so right there I decided to try and get a knowledge of what I was looking at to some extent, and studied all the books in our Peterboro Public Library including government mineral reports of all kinds but, one book I acquired and I think I got it from your department, was called 'Prospecting for Uranium and Thorium in Canada' which gave me the information which resulted in my finding the original showing at Bicroft. In an old report in the library here which was printed I think in 1912 on the mineral mica I read of a showing in Cardiff Twp. composed of very large plates of phlogopite and went to Mr. Howard Sarginson to see if he could tell me where this old pit was as he lived on adjoining lot, but he had never saw nor heard of it, but was willing to go with me to show me Centre Lake which I had never been to. As we were walking along an old wagon road I saw where a wheel of a steel rimmed wagon had slipped across the face of a rock exposure and it was covered with a purplish coloured dust and upon chipping it with my hammer found it to be very deep purple fluorspar and by the book (Prospecting for Uranium and Thorium) the colour was due to a radioactive mineral in the same vicinity, and at the next exposure about 75 yards north I found a crystal about t inch diameter completely surrounded by radial fractures of 1-2 inches in length which the same book said was caused by the radioactivity of the crystal inside the fractures, I dug the crystal out and brought it home and the next day went back with my son and looked around some more and found several nice surface samples which due to colour of oxide on them I thought must be associated with uranium, but I did not own a geiger counter and only knew where there was one in Peterboro which was owned by Mr. Robert Steele so I took my samples to him to have them checked on his counter and he said they read very high and could we get together and get some ground staked in partnership before the news got out, which we started to do the next day but as neither of us had ever staked a claim before we did not get as much ground covered as we should have, due to being too painstaking in sighting lines, measuring claims, etc. and then the word got out and we were surrounded by staked claims so we rented a Warsop rock drill and blew out some trenches from which we sent samples to your department for mineral identification and among which were uraninite."[5]

In late 1952, Mr Burns sold his property to a Toronto syndicate that formed into the Centre Lake Uranium Mines Limited, lead by C. C. Huston. The company worked on the surface, opened an adit and started diamond drilling, mostly to 100 feet, sometimes to 50 feet. A shaft was created in 1954. Simultaneous to this, Croft Uranium Mines Limited, a subsidiary of Macassa Lines Limited formed in 1953. They discovered uranium north of the original site. In 1955 the two sites were merged under the ownership of Bicroft Uranium Mines Limited, with work centering around the Centre Lake part of the property. A shaft was sunk to 1,300 feet and ten levels created. The treatment plant capable of processing 1,000 tons of ore a day was built and operations started in late 1956. 1957 production was 414,024 tons per day, valued at $18.92 per ton. Production increased to 1,300 a day in 1958 and exploration started to the south of the site.[5]

The mine employed up to 500 people at its peak.[9]

Mining continued until 1963 producing a total of 2,470,000 tonnes of uranium ore.[10] 2,284,421 tonnes of tailings remain on site in two impoundments.[11]

Repairs to the decommissioned site, included adding vegetation over the tailings, were completed in 1980. Subsequent upgrades of the dams was completed in the 1990s.[12][13][14] The site is now a wetlands.[15]

The geology of Bicroft mine was described by Geological Survey of Canada in 1962[5] as follows:

"The deposits are in a northerly trending belt of paragneiss and amphibolite forming the east flank of the Centre Lake granite sheet, which is part of the Cardiff plutonic complex described the rocks of the favourable zone as biotite paragneiss, amphibolite, scapolite-biotite gneiss, garnet-sillimanite-biotite paragneiss, and a narrow band of silicated marble. These are intruded and replaced by lenticular 'dykes' of both sodic and potassic syenite and granite and related rocks in a zone about half a mile wide extending for about 3.5 miles. Satterly stated that it appears to be terminated to the north by a fault. The 'dykes' range from a few feet to 80 feet in width and from a few feet to 400 feet in length. They are arranged in an en échelon fashion, striking northerly and dipping from 40° to 70°E, commonly transgressing slightly the attitude of the host rocks. The ore minerals are uranothorite and uraninite, accompanied locally by allanite, zircon, titanite, apatite, fluorite, pyrite, pyrrhotite and molybdenite. Satterly listed pyrochlore, betafite anatase and umangite as rare accessory minerals. Mafic minerals are pyroxene and biotite, some bodies containing considerable pyroxene. In contrast to the mafic shoots at the Faraday mine, those at the Bicroft contain little magnetite. Red alteration occurs locally, particularly at contacts with sillimanitegarnet-biotite gneiss and where reddish feldspar is present in amphibolite. Uranium to thorium ratios vary in different bodies, thorium being more abundant in the pyroxene granite."[5]

Arthur H. Shore, an independent prospector, first found uranium at his lot on Faraday township in 1948 or 1949. He founded Faraday Uranium Mines Limited in 1949, but injured himself shortly afterwards. Newkirk Mining Corporation lead work in 1952, including diamond drilling in December 1952 which helped identify seven main zones of uranium ore. 1953 drilling discovered more uranium up to 500 feet underground. 1954 drilling found more uranium and adits were created. By 1955 it was established that there was 1,660,980 tons of ore that was 0.112% U₃O₈. A sale price was agreed in January 1956. A 863 feet deep shaft was sunk from an adit, from which five levels were established. A treatment plant with a 750 ton-per-day capacity was built and operations started in April 1957. In 1958, the treatment capacity was increased to 1,350 tons per day in order to support processing of ore from Greyhawk Mine. 1957 production or uranium was 405,271 pounds of ore that was 0.0859% U₃O₈.[5] Between 1948 and 1964 Faraday Mine had produced $54 million of ore.[1]

After $7 million of investment to rehabilitate the mine,[1] it reopened as the Madawaska Mine in 1975 and production continued to 1982. The shaft into the uranium-bearing pegmatite reached a depth of 473 metres (1,552 ft).[16] During this period, the mine was producing 1,500 ton of ore per day.[1]

Since inspections found improper surface protection of tailing in 2015, the mine has been undergoing rehabilitation.[13]

The geology of Faraday Mine/Madawaska Mine mine was described by Geological Survey of Canada in 1962[5] as follows:

"The deposits are in a belt of metagabbro and amphibolite on the south flank of the Faraday granite. These mafic rocks strike east and dip fairly steeply to the south.

The orebodies are parts of a system of pegmatitic granite dykes found at intervals over a distance of about 6,000 feet and a width of several hundred feet. Some of the material in the dykes appears to be of metasomatic origin. The predominant trend is N70 °E, with fairly regular dips of 50° to 60 °SE (staff of Faraday Uranium Mines, 19 57). Dips are commonly flatter, however, in the lower levels. The dykes are irregular in shape, and the lenticular ore shoots within them are even more irregularly and erratically distributed. The average stoping width was stated to be 17 feet, and the maximum sustained stoping width 60 feet. Close study by mine geologists, use of portable counters underground, and unusually careful car sampling were used to control the grade of material mined.

An orebody may consist of a series of irregular lenses of better-grade material. Ore shoots commonly occur at the margins of a mass of pegmatitic granite. In some places the bodies conform with the attitude of the host rock, even following structures that appear to be minor folds, and in other places they transgress the host rock. The staff reported that no consistent control over pegmatite emplacement had been noted, that folding or faulting later than the pegmatitic granite had not been recognized, and that fractures are rare although lenses of recrystallized breccia had been found locally.

The principal ore minerals are uraninite and uranothorite. Other radioactive minerals are allanite, cyrtolite, uranophane and beta-uranophane, and rare earth minerals containing cerium and lanthanum. The uranium to thorium ratio is about 2 to l. Satterly (1957, p. 111) stated that the rocks of the ore shoots are leucogranite, pyroxene granite (or syenite )-pegmatite, and magnetite or magnetitepyroxene bodies in 'pegmatite'. The staff reported that criteria for the presence of orebodies include hematite staining; abundant ferromagnesian minerals, including augite and hornblende; the presence of large tabular inclusions of country rock; and frequently the presence of magnetite, particularly in the richer zones. One of the last-named mafic bodies, about 13 feet wide and 240 feet long and reported to average 0.40 per cent U 30 8 , occurred in the upper part of the mine (see Fig. 17, largest body) and was responsible for early high-grade intersections. It provided rich ore for blending with lower-grade material, some of which was reported to contain only 0.07 per cent U₃O₈."[5]

Prospector Paul Mullette discovered radioactive occurrences in November 1953 that were sold to Dyno Mines Limited, who later changed their name to Canadian Dyno Mines Limited. The company undertook diamond drilling that same month simultaneous to geological mapping. This identified three zones, resulting in drilling, which discovered two more zones. Surface diamond drilling of 124 holes at 200 feet intervals occurred through 1954 and 1955. A 1,000 feet shaft, in the "B" zone, was sunk creating five levels. A price to sell uranium was agreed, an ore treatment plant with 1,000 tons per day capacity was started in 1956. Production started in May 1958.[5]

The geology of Dyno mine was described by Geological Survey of Canada in 1962[5] as follows:

The deposits are in a belt of paragneiss, para-amphibolite, and other rocks at the east flank of the Cheddar granite, striking about N25 °W and dipping about 50°E. The host rock of the orebodies is commonly biotitehornblende-feldspar gneiss.

The orebodies and potential ore zones consist of a series of northerly striking pegmatitic granite dykes, dipping about 50°E. They are nearly conformable with their metasedimentary host rocks but crosscutting relationships can be seen locally. The five zones are almost in line and may be connected at depth. Each zone contains numerous branching dykes of different widths, but all are lenticular.

All dykes are not of ore grade, and the widest rarely contain ore. Dykes that do contain ore may do so only in certain parts.

The dyke system on which the shaft was sunk was explored extensively for a length of 800 feet and to a depth of more than 1,000 feet, dykes being from 3 to 60 feet wide. Vallance and Skrecky (1957) reported that "where the dykes are narrow, in the order of 12 feet or less, mineable grade across the full dyke width exists. In the wider dykes, only a portion of the dyke may contain a sufficient concentration of uraniferous minerals to make ore grade. Such lenses are not confined to any single portion of the dyke and may occur in the centre or along either wall or cross from one wall to the other. Tenor of ore within the lenses varies from 0.05 per cent U3 0 8 to in excess of 1.00 per cent U3 0 8 ." Two sets of narrow fractures have been observed. One set strikes N20 °W and the other strikes nearly north; the ore is nearly always associated with the latter.

The uranium-bearing minerals are uraninite and uranothorite. Other radioactive minerals are allanite and cyrtolite. Peristerite and magnetite are common in the ore. The ore of higher grade usually exhibits a dark red coloration and an increase in magnetite content. Underground exploration was said to have revealed better grades and tonnages than were indicated by drilling. Ore reserves were estimated by the company to average 0.093 per cent U₃O₈."[5]

Radioactive materials were first discovered in Faraday Township in 1955 by K. D. Thompson and M. Card, two employees of Goldhawk Porcupine Mines Limited who were surveying with geiger counters. Messrs. Thompson and Card found exposed rock in a 60-foot by 300-foot area. Diamond drilling followed at 50 to 400 feet intervals at 450 feet depth. A shaft was sunk in 1956 and three levels created.[5]

Ore was transferred for processing at the Faraday Mine site, starting August 1957 at a rate of about 200 tons per day. By the end of 1957, 19,568 tons at a value of $11.40 per ton was shipped. Through 1958 production was 150 tons per day averaging at 0.082% U₃O_8.[5]

Ownership subsequently shifted to Goldhawk Porcupine Mines Limited.[5]

Mining operations stopped in 1959.[1][13]

Faraday Uranium Mines Limited purchased the site in 1962.[17][18]

Madawaska Mines Limited was formed in 1975 and purchased the mine, as well as the Faraday Mine. Mining operations restarted in 1976 and continued until 1982.[17][4]

The geology of Greyhawk mine was described by Geological Survey of Canada in 1962[5] as follows:

"The zone consists of easterly striking dykes of pegmatitic granite intruding metagabbro. The dykes, which pinch and swell, vary in width from 1 foot to 60 feet, dip 30° to 60°S, and generally follow the gneissosity of the country rock. Inclusions of wall-rocks lie here and there within the dykes. The ore minerals are uraninite and uranothorite. The ore shoots within the dykes have an average length of about 100 feet, an average width of 6 feet, and a slope depth of from 50 to 100 feet. Higher concentrations of radioactive minerals occur where the host rock is richer in mafic minerals and where it is much fractured; most dykes and ore zones within the dykes are narrower than those at Bicroft; variable amounts of chlorite occur with the ore; the ore is never found in the metagabbro but commonly in contact with it; no high grade deposits have been found to date, and the average grade of the ore is probably slightly lower than that at other orebodies being mined in the Bancroft camp. Fockler (personal communication) stated that the development grade was about 10 per cent below the grade indicated by surface diamond drilling, and that the tonnage outlined in underground development work, as of November 1, 1957, was about 30 per cent below the tonnage indicated by surface diamond drilling...The ore was reported in 1957 to average 0.095 per cent U₃O₈."[5]

After mining, the uranium ore was treated in acid leaching plants located at the mines. The leaching process produced "yellowcake" high-grade uranium compounds which were either process further at the Port Hope refinery or sold to USA government for processing there. Processing uranium ore in Bancroft cost $3.00 per ton.[6]

Eldorado Mining and Refining Limited was the crown company that purchased all uranium oxide in Canada and it entered into contracts with mine owners at fixed prices.[19]

Faraday Mine alone produced $54 million of uranium ore, creating a rapid economic boom. Mine workers unionized in 1957, forming Local 1006 Bancroft Mine and Mill Worker's Union.[1]

The success of the mine was due to a combination of factors, and not simply because of Arthur Shore's discovery of uranium. The factors that resulted in economically viable mines were Bancroft's geographical proximity to industrial centers (Port Hope), a good road and rail network.[20]

Employment of miners in Bancroft started in 1955, peaked in 1958 at around 1,600 jobs.[19]

Housing for miners was quickly established around the mines and in nearby Bancroft village, which extended to cover four square miles. Other construction quickly followed, including, two single-men's bunkhouses, a canteen, an eleven-room school, an ice-curling rink, and a recreation center. In 1957 a swimming pool was started.[21]

The combination of a global decline in demand for uranium (specifically the cancellation of a contract to buy by Agip[22]) combined with the more efficient extraction occurring in Ontario near Elliot Lake,[20] closed the remaining mines in 1964 destroying the local economy. Local catholic priest Rev. Henry Maloney, whose two brothers were former Ontario Ombudsman Arthur Maloney, and Minster of Mines James Anthony Maloney, led the community to demand support from the Government of Ontario and Government of Canada to extend the contracts for buying uranium. Canadian Prime Minister John Diefenbaker, relying on a old agreement with the United Kingdom to buy uranium from Canada, was able to prolong the life of the mine by eighteen months, giving the community enough time to plan for the closure.[1]

After the closure of the mines, the various tailing site attracted mineral collectors, especially to an annual "gemboree" in which tourists travelled to Bancroft in search of gems and minerals.[1][24]

200,000 tons of ore, averaging 0.065% U₃O₈, remain in the ground at Greyhawk Mine.[17] Dyno Mine ran out of uranium ore in 1960.[21]

In 2007, the Globe and Mail newspaper reported on a $3 million uranium development project in nearby Haliburton.[25]

1978 and 1980 studies found that the natural weathering of the granite and gabbro rocks left on at Greyhawk Mine has caused uranium leaching into the aquifer at concentrations ranging between 1.2 to 380 parts per billion, with higher concentrations measured deeper in the water table and in sediments.[26][27]

Tailings remain at Bicroft, Madawaska and Dyno sites where water sampling by the Canadian Nuclear Safety Commission is ongoing.[8] 2019 sampling found radioactive and hazardous contamination in two of several water samples.[13] Subsequent inspections in 2020 from nearby locations reported no contamination.[28]

Dyno, Greyhawk, and Madawaska Mines are now managed by E.W.L Management Limited[13] (a subsidiary of Ovintiv[29]). Bicroft Mine is owned by Barrick Gold; the owners of all legacy tailing sites at former mines are responsible for the ongoing management of the sites.[13]

In the 1970s, the scientific community was making connections between uranium mining and silicosis in miners. Uranium mining produces silica-laden dust and the health risk to miners is correlated to the amount of free silica in the uranium ore. Whereas the uranium mines in Elliot Lake produced ore with a free silica rate of 60 to 70 per cent, the dust from the miners around Bancroft had 5 to 15% free silica, thus presenting some risk to miners, but much less than that of the Elliot Lake's uranium mines. In 1974, the Ontario Workmen's Compensation Board studied 15,094 people who worked in uranium mines in Bancroft and around Elliot Lake for at least one month, between 1955 and 1974. Of those 15,094 people, 94 silicosis cases were found in 1974, of which one was attributable to working a Bancroft mine - i.e. the other 93 were attributable to working in an Elliot Lake mine.[19]

Mines produce radon gas which can increase lung cancer risks. Miners exposure to radiation was not measured before 1958 and exposure limits were not enacted until 1968. Risks to miners at Bancroft and Elliot Lake mines were investigated and the official report of that investigation quotes a miner:[19]

"We have been led to believe through the years hat the working environment in these mines was safe for us to work in. We have been deceived."[19]

The aforementioned 1974 study of 15,094 Ontario uranium miners found 81 former miners who died of lung caner. Factoring in predicted lung cancer rate for men in Ontario, led to the conclusion that by 1974 there were 36 more deaths than expected attributable to both Bancroft and Elliot Lake mines, with the additional risk being twice as high for Bancroft miners compared to Elliot Lake miners.[19]

A 2015 report on study commissioned by the Canadian Nuclear Safety Commission and undertaken by the Occupational Cancer Research Centre at Cancer Care Ontario tracked the health of 28,959 former uranium miners over 21 years and concluded that:

"There was about a two-fold increase in the risk of lung cancer mortality (RR= 2.32, 95% CI: 1.72-3.14) and lung cancer incidence (RR=1.89, 95% CI: 1.43-2.50) with a five year lag interval incorporated in the highest cumulative exposure category of >100 WLM. For lung cancer mortality, this relationship was modified by attained age, time since first exposure, time since last exposure, exposure rate, age at first exposure, and dose rate. For lung cancer incidence, this relationship was modified by time since first exposure, time since last exposure and exposure rate."[30]

The BMJ reported:

"An increased risk of lung cancer and a dose–response relationship was observed with cumulative radon exposure. Miners exposed to >100 WLM demonstrated a twofold increase in the risk of lung cancer incidence (RR=1.89, CI 1.43 to 2.50)."[31]

The study will be updated in 2023.[32]