Tanco Mine or Bernic Lake mine is an underground caesium and

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...

mine, owned and since 2019 owned and operated by Sinomine Resource Group on the north west shore of

Bernic Lake Bernic Lake is a lake in the eastern part of the province of Manitoba, Canada. It is located just southwest of Nopiming Provincial Park, and just north of Whiteshell Provincial Park. The Tanco mine is located on the northwestern shore of the rive ...

Manitoba , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , coordinates = , capital = Winn ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

. The mine has the largest known deposit of

pollucite Pollucite is a zeolite mineral with the formula with iron, calcium, rubidium and potassium as common substituting elements. It is important as a significant ore of caesium and sometimes rubidium. It forms a solid solution series with analcime. ...

and is also the world's largest producer of caesium. The mine has the largest

reserves in

having estimated reserves of 2.1 million tonnes of ore grading 0.22%

. The mine also has additional reserves amounting to 7.3 million tonnes of ore grading 2.76%

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...

. The mine also produces caesium brine, which is converted into caesium formate which is used mostly as additive for drilling fluids to increase the fluid's

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

. A concentrated solution of caesium formate has a density of 2.3 g/cm³.

History

The pegmatite ore body now mined by the Tanco Mine was discovered in the late 1920s and the first mining started in 1929. Several times the mine was closed, reopened and closed, until in 1969 when it was reopened as a

mine.

Cabot Corporation Cabot Corporation is an American specialty chemicals and performance materials company headquartered in Boston, Massachusetts. The company operates in over 20 countries with 36 manufacturing plants, eight research and development facilities and ...

bought the mine in 1993, and began the production of caesium brine from

in 1996. Tanco Mine was purchased by Sinomine in June 2019. Sinomine paid $135 million with an additional 10-year lithium royalty consideration. Tax impact was unexpected.

Geology

The pegmatite found at the north west shore and below the lake floor of Bernic Lake is a

granitic A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

enriched in the

incompatible element In petrology and geochemistry, an incompatible element is one that is unsuitable in size and/or charge to the cation sites of the minerals of which it is included. It is defined by the partition coefficient between rock-forming minerals and melt b ...

s, for example caesium, lithium, tantalum and beryllium. Pegmatite forms if

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

tic rock slowly crystallizes, and the incompatible elements are concentrated in the residual molten magma. Examples of minerals found in the mine are the lithium-containing spodumene and amblygonite, caesium-containing

, beryllium-containing

beryl Beryl ( ) is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several ...

and tantalum- and niobium-containing simpsonite and tantalite.

Deposit

The

(chemical formula ) deposit associated with the pegmatite is the largest known deposit of this mineral and with 350,000 tons, it accounts for two thirds of the known resources. With an estimated average global use of 30,000 kg/year the reserves of the mine would last for 2,000 to 3,000 years. The mined pollucite contains approximately 24% . The ore body is 1400 m long, 600 m wide and 100 m deep. For several decades the pegmatites at Bernic Lake have supplied the world with the needed caesium.

History

Geology

Deposit

References

Further reading