Tanco Mine
Encyclopedia
Tanco Mine is an underground caesium
and tantalum
mine
, owned and operated by Cabot Corporation
on the north west shore of Bernic Lake
, Manitoba
, Canada
. The mine has the largest known deposit of pollucite
and is also the world's largest producer of caesium
.
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 tantalum
mine. Cabot Corporation bought the mine in 1993, and began the production of caesium brine
from pollucite
in 1996. The caesium brine is converted into caesium formate which is used mostly as additive for drilling fluids to increase the fluid's density
. A concentrated solution of caesium formate has a density of 2.3 g/cm3.
enriched in the incompatible element
s, for example caesium, lithium, tantalum and beryllium. Pegmatite forms if magma
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 pollucite
, beryllium-containing beryl
and tantalum- and niobium-containing simpsonite
and tantalite
.
((Cs,Na)2Al2Si4O12·2H2O) 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% Cs2O. 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.
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
and tantalum
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...
mine
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
, owned and operated by Cabot Corporation
Cabot Corporation
Cabot Corporation is a specialty chemicals and performance materials company. It operates in four segments: the Carbon Black Business, the Metal Oxides Business, the Supermetals Business, and the Specialty Fluids Business. Cabot's headquarters is located in Boston, Massachusetts...
on the north west shore of Bernic Lake
Bernic Lake
Bernic Lake is a lake in the province of Manitoba, Canada.The Tanco mine is located on the northwestern shore of the river. The mine is an active producer of caesium, tantalum and spodumene from a large pegmatite ore body....
, Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. The mine has the largest known deposit of pollucite
Pollucite
Pollucite is a zeolite mineral with the formula 2Al2Si4O12·2H2O 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. It crystallizes in the isometric -...
and is also the world's largest producer of caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
.
History
The pegmatitePegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
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 tantalum
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...
mine. Cabot Corporation bought the mine in 1993, and began the production of caesium brine
Brine
Brine is water, saturated or nearly saturated with salt .Brine is used to preserve vegetables, fruit, fish, and meat, in a process known as brining . Brine is also commonly used to age Halloumi and Feta cheeses, or for pickling foodstuffs, as a means of preserving them...
from pollucite
Pollucite
Pollucite is a zeolite mineral with the formula 2Al2Si4O12·2H2O 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. It crystallizes in the isometric -...
in 1996. The caesium brine is converted into caesium formate which is used mostly as additive for drilling fluids to increase the fluid's density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
. A concentrated solution of caesium formate has a density of 2.3 g/cm3.
Geology
The pegmatite found at the north west shore and below the lake floor of Bernice Lake is a granitic igneous rockIgneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
enriched in the incompatible element
Incompatible element
An incompatible element is a term used in petrology and geochemistry to describe an element that is unsuitable in size and/or charge to the cation sites of the minerals, and is defined by the partition coefficient between rock-forming minerals and melt being much smaller than 1..During the...
s, for example caesium, lithium, tantalum and beryllium. Pegmatite forms if magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
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
Spodumene
Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate, LiAl2, and is a source of lithium. It occurs as colorless to yellowish, purplish, or lilac kunzite , yellowish-green or emerald-green hiddenite, prismatic crystals, often of great size...
and amblygonite
Amblygonite
Amblygonite is a fluorophosphate mineral, AlPO4, composed of lithium, sodium, aluminium, phosphate, fluoride and hydroxide. The mineral occurs in pegmatite deposits and is easily mistaken for albite and other feldspars. Its density, cleavage and flame test for lithium are diagnostic. Amblygonite...
, caesium-containing pollucite
Pollucite
Pollucite is a zeolite mineral with the formula 2Al2Si4O12·2H2O 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. It crystallizes in the isometric -...
, beryllium-containing beryl
Beryl
The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare...
and tantalum- and niobium-containing simpsonite
Simpsonite
Simpsonite has a general formula of Al43O13. It occurs as euhedral to subhedral tabular to short and prismatic crystals, commonly in subparallel groups. Under the petrographic microscope it has a very high relief....
and tantalite
Tantalite
Tantalite, [2O6], is a mineral group that is close to columbite. The two are often grouped together as a semi-singular mineral called coltan or "columbite-tantalite" in many mineral guides. However, tantalite has a much greater specific gravity than columbite...
.
Deposit
The pollucitePollucite
Pollucite is a zeolite mineral with the formula 2Al2Si4O12·2H2O 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. It crystallizes in the isometric -...
((Cs,Na)2Al2Si4O12·2H2O) 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% Cs2O. 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.