Sala Silvermine
Encyclopedia
Sala Silver Mine is a mine in Sala Municipality, in Västmanland County
in Sweden
. The mine was in continuous production from the 15th century until 1908. Additional mining occurred in 1950-1951 and also in 1945-1962 in Bronäs Mine, located nearby. The Sala ore is mainly known for its high silver
content though the ore also contained economic amounts of lead
and zinc
. The zinc was hosted by the mineral sphalerite
while lead was hosted by the mineral galena
. Silver occurred as a native phase rarely but was mainly hosted by complex antimonide
s and sulphosalts, dispersed in the matrices of galena and sphalerite, invisible to the naked eye but visible in microscope. The silver content in typical galena-dominated Sala ore was about 0.15% to 1%, the latter being one of the highest contents of silver in galena ever reported. In the sphalerite-dominated ore, the silver content is only about 0.015-0.02%, which was still enough to exploit and would even be at present days, given that a sufficient tonnage of metallurgically advantageous ore could be found.
The mine has had three major heydays, the main one in early 16th century, a second less significant one in the mid-17th century and a last one in the late 19th century. The last period involved re-organisation of the mine organisation (a transition from state-owned to company-owned) as well as the introduction of several new technological innovations, e.g. leaching
methods employed on older mine tailings. These innovations produced temporal production peaks, yet a general lack of high-grade ore made continued production uneconomic which finally led to closure. At most, 3-5 million tons of rock were mined from which ~ 450 tons of silver and about 35 000 tons of lead were extracted. The maximum depth of the mine is 318.6 m and the length of the mine is ~ 700 metres, the width is ~ 100 m.
The town of Sala
emerged as a miners settlement near the mine, first in the form of a small mining village in the early days, then moved to its present location on order from the king. The king Gustavus Adolphus of Sweden
gave the town its privileges in 1624. Around Sala there are numerous lakes and dams with canals, constructed to supply the mine with hydro-power for driving machines for water pumping, ore hoisting and ore smelting. None of these machines are preserved to present days.
The bedrock was created about 1,89 billion years ago during the paleoproterozoic
era
. The host rock to the mined ore is dominated by white dolomitic
marble
, proximal to the ores commonly rich in skarn
minerals such as tremolite
, serpentine, diopside
and chlorite
, giving the dolomitic marble at Sala a characteristic green colour. ~ 100 meters away from the mine, more pure white dolomitic marble poor in skarn minerals is extracted at the Tistbrottet dolomite quarry. Earlier, granite
('Sala granite') was extracted to be used as bricks for construction material northeast of the mine. Several foundations for the buildings in the mine area are built from Sala granite.
and Avesta Jernverks AB that until 1962 extracted lead and zinc and very little silver. The extraction was made in a mine not physically connected to the old mine. Since 1988 is the mine owned by the municipality of Sala and works as a mine museum.
Above ground, the old buildings are still used, but today mostly for souvenir shops and museums, like an art gallery and a police museum. In July every year, the Mine's days are arranged and in December there are Christmas markets every weekend until Christmas.
In march of 2008, the mine was visited by the Swedish crown princess Victoria, who left her signature down in the mine as her father, Carl XVI Gustav of Sweden, had done previously.
Västmanland County
Västmanland County is a county or län in central Sweden. It borders to the counties of Södermanland, Örebro, Gävleborg, Dalarna and Uppsala...
in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
. The mine was in continuous production from the 15th century until 1908. Additional mining occurred in 1950-1951 and also in 1945-1962 in Bronäs Mine, located nearby. The Sala ore is mainly known for its high silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
content though the ore also contained economic amounts of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
and zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
. The zinc was hosted by the mineral sphalerite
Sphalerite
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
while lead was hosted by the mineral galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
. Silver occurred as a native phase rarely but was mainly hosted by complex antimonide
Antimonide
Antimonides are compounds of antimony with more electropositive elements. The antimonide ion is Sb3−.Many of them are flammable or decomposed by oxygen when heated since the antimonide ion is a reducing agent....
s and sulphosalts, dispersed in the matrices of galena and sphalerite, invisible to the naked eye but visible in microscope. The silver content in typical galena-dominated Sala ore was about 0.15% to 1%, the latter being one of the highest contents of silver in galena ever reported. In the sphalerite-dominated ore, the silver content is only about 0.015-0.02%, which was still enough to exploit and would even be at present days, given that a sufficient tonnage of metallurgically advantageous ore could be found.
The mine has had three major heydays, the main one in early 16th century, a second less significant one in the mid-17th century and a last one in the late 19th century. The last period involved re-organisation of the mine organisation (a transition from state-owned to company-owned) as well as the introduction of several new technological innovations, e.g. leaching
Leaching (metallurgy)
Leaching is a widely used extractive metallurgy technique which converts metals into soluble salts in aqueous media. Compared to pyrometallurgical operations, leaching is easier to perform and much less harmful, because no gaseous pollution occurs...
methods employed on older mine tailings. These innovations produced temporal production peaks, yet a general lack of high-grade ore made continued production uneconomic which finally led to closure. At most, 3-5 million tons of rock were mined from which ~ 450 tons of silver and about 35 000 tons of lead were extracted. The maximum depth of the mine is 318.6 m and the length of the mine is ~ 700 metres, the width is ~ 100 m.
The town of Sala
Sala, Sweden
Sala is a locality and the seat of Sala Municipality in Västmanland County, Sweden with 12,059 inhabitants in 2005.- History :The small town is best known for its historical silver mine, which dates back to at least Medieval times, and was in operation until 1908...
emerged as a miners settlement near the mine, first in the form of a small mining village in the early days, then moved to its present location on order from the king. The king Gustavus Adolphus of Sweden
Gustavus Adolphus of Sweden
Gustav II Adolf has been widely known in English by his Latinized name Gustavus Adolphus Magnus and variously in historical writings also as Gustavus, or Gustavus the Great, or Gustav Adolph the Great,...
gave the town its privileges in 1624. Around Sala there are numerous lakes and dams with canals, constructed to supply the mine with hydro-power for driving machines for water pumping, ore hoisting and ore smelting. None of these machines are preserved to present days.
The bedrock was created about 1,89 billion years ago during the paleoproterozoic
Paleoproterozoic
The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
era
Era
An era is a commonly used word for long period of time. When used in science, for example geology, eras denote clearly defined periods of time of arbitrary but well defined length, such as for example the Mesozoic era from 252 Ma–66 Ma, delimited by a start event and an end event. When used in...
. The host rock to the mined ore is dominated by white dolomitic
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
marble
Marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...
, proximal to the ores commonly rich in skarn
Skarn
Skarn is an old Swedish mining term originally used to describe a type of silicate gangue, or waste rock, associated with iron-ore bearing sulfide deposits apparently replacing Archean age limestones in Sweden's Persberg mining district. In modern usage the term "skarn" has been expanded to refer...
minerals such as tremolite
Tremolite
Tremolite is a member of the amphibole group of silicate minerals with composition: Ca2Mg5Si8O222. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades...
, serpentine, diopside
Diopside
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class...
and chlorite
Chlorite group
The chlorites are a group of phyllosilicate minerals. Chlorites can be described by the following four endmembers based on their chemistry via substitution of the following four elements in the silicate lattice; Mg, Fe, Ni, and Mn....
, giving the dolomitic marble at Sala a characteristic green colour. ~ 100 meters away from the mine, more pure white dolomitic marble poor in skarn minerals is extracted at the Tistbrottet dolomite quarry. Earlier, granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
('Sala granite') was extracted to be used as bricks for construction material northeast of the mine. Several foundations for the buildings in the mine area are built from Sala granite.
Owner
The mine was owned during later years by AB Svenska Metallverken in VästeråsVästerås
Västerås is a city in central Sweden, located on the shore of Lake Mälaren in the province Västmanland, some 100 km west of Stockholm...
and Avesta Jernverks AB that until 1962 extracted lead and zinc and very little silver. The extraction was made in a mine not physically connected to the old mine. Since 1988 is the mine owned by the municipality of Sala and works as a mine museum.
The mine today
Today the mine functions mostly as an attraction, where guided tours down in the mine are arranged. In the big empty rooms in the mine, concerts and other entertainment are arranged. New test-drillings have been made lately, because it is believed that a second silver treasury exists around the old one. Already during the 18th century did people search for the second treasury, but its depth makes it hard to find. Around the old mine, cracks and erosions have caused danger for people visiting restricted areas.Above ground, the old buildings are still used, but today mostly for souvenir shops and museums, like an art gallery and a police museum. In July every year, the Mine's days are arranged and in December there are Christmas markets every weekend until Christmas.
In march of 2008, the mine was visited by the Swedish crown princess Victoria, who left her signature down in the mine as her father, Carl XVI Gustav of Sweden, had done previously.