Tschermakite
Encyclopedia
The endmember hornblende
tschermakite (Ca
2(Mg
,Fe
2+)3Al2(Si
6Al2)O
22(OH
)2) is a calcium rich monoclinic amphibole
mineral. It is frequently synthesized along with its ternary solid solution series members tremolite
and cummingtonite
so that the thermodynamic properties of its assemblage can be applied to solving other solid solution series from a variety of amphibole minerals.
, K
, Mn
; Y=Mg, Fe+2 ,Fe+3, Al, Ti
, Mn, Cr
, Li
, Zn
; Z=Si, Al (Deer et al., 1963). The structure of tremolite
(Ca2Mg5(Si8O22)(OH,F
)2), another calcic amphibole, is commonly used as the standard for calcic amphiboles from which the formulae for their substitutions are derived. The wide range in variety of minerals classified in the amphibole group is due to its great ability for ionic replacement resulting in a widely varying chemical composition. Amphiboles can be classified on the basis of the substitution of ions on the X site as well as the substitution of AlAl for Si(Mg, Fe+2). In the calcium amphiboles like tschermakite Ca2(Mg, Fe2+)3Al2 (Si6 Al2) O22(OH)2, the predominant ion in the X position is occupied by Ca as in tremolite, while the substitution MgSi<->AlAl occurs on the Y and the tetrahedral Z site.
s and ultramafic igneous rock
s as well as in medium to high-grade metamorphic rock
s. The mineral is widespread throughout the world but has most notably been studied in Greenland
, Scotland
, Finland
, France
, and the Ukraine
(Anthony, 1995). Because amphibole minerals like Tschermakite are hydrous (contain an OH group), they can break down to denser anhydrous minerals like pyroxene
or garnet
at high temperatures. Conversely, amphiboles can be recomposed from pyroxenes as a result of crystallizing igneous rocks as well as during metamorphism (Léger and Ferry, 1991). Because of this important quality, P-T conditions have repeatedly been calculated for the crystallization of hornblendes in calc-alkaline magmas (Féménias et al., 2006). In addition to studying tschermakitic content in its natural occurrences, geologists have frequently synthesized this mineral in order to further calculate its place as an endmember hornblende.
Tschermakite received its name in honor of the Austrian mineralogist Professor Gustav Tschermak von Seysenegg
(1836-1927) whose mineral textbook Lehrbuch der Mineralogie (orig. pub.1883) was described as the German language equivalent to the works of Edward Salisbury Dana
(Mineralogy 1885).
In 1872 Professor Tschermak founded one of Europe’s oldest geoscience journals Mineralogische Mitteilungen (Deu: Mineralogical Disclosures) or Mineralogy
and Petrology
. In the first volume of Min. Mitt., Tschermak established some of the early classifications of the amphibole group in relation to the pyroxene group of minerals (Tschermak 1871), which no doubt led to the formula Ca2Mg3Al4Si6O22(OH)2 being known as the Tschermak molecule, this mineral formula was later assigned the name tschermakite as first proposed by Winchell (1945).
Professor Tschermak spent many years working as curator for the Imperial Mineralogical Cabinet. The Mineralogical Dept. of the Imperial Natural History Museum
in Vienna – an impressive mineral, meteorite and fossil collection has Professor Tschermak to thank for his detailed inventory system that has helped preserve it to this day as well as the expansion of their meteorite collection. He was a full professor of mineralogy and petrography at the University of Vienna
as well as a full member of the Imperial Academy of Sciences in Vienna
. He was also the first president of the Viennese (now Austrian) Mineralogical Society, founded in 1901.
An obituary for “Hofrat Professor Dr. Gustav Tschermak” written by Edward S. Dana (1927) can be found in the 12th volume of American Mineralogist where Dana recalls the two young scientists earlier work together in the Vienna Mineral Cabinet and remarks on Professor Tschermak’s vigor and clarity of mind maintained up to his final days. Gustav Tschermak’s third child, Erich von Tschermak
-Seysenegg (1871-1962) was a renowned botanist who is credited for independently resdiscovering Gregor Mendel
’s genetic laws of inheritance by working with similar plant breeding experiments.
s and tschermakite both belong to the latter crystal structure
. The crystal group of tschermakite is 2/m.
Tschermakite and all the hornblende varieties are inosilicates, and like the other rock forming amphiboles are double chain silicates (Klein and Hurlbut, 1985). The amphibole structure is characterized by it’s two double chains of SiO4 tetrahedra (T1 and T2) sandwiching in a strip of cations (M1, M2 and M3 octahedra). Much of the discussions and studies of both tschermakite and tremolite have been to resolve the varying cation placements and Al substitutions that seem to occur on all T and M sites (Najorka and Gottschalk, 2003).
will be brittle to conchoidal. In thin section
its optic sign and 2V angle cover a wide range and are not very useful for identification. It shows a distinct pleochroism
in browns and greens.
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
tschermakite (Ca
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
2(Mg
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
,Fe
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
2+)3Al2(Si
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
6Al2)O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
22(OH
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
)2) is a calcium rich monoclinic amphibole
Amphibole
Amphibole is the name of an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures.-Mineralogy:...
mineral. It is frequently synthesized along with its ternary solid solution series members 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...
and cummingtonite
Cummingtonite
Cummingtonite is a metamorphic amphibole with the chemical composition 7Si8O222, magnesium iron silicate hydroxide.Monoclinic cummingtonite is compositionally similar and polymorphic with orthorhombic anthophyllite, which is a much more common form of magnesium-rich amphibole, the latter being...
so that the thermodynamic properties of its assemblage can be applied to solving other solid solution series from a variety of amphibole minerals.
Mineral composition
Tschermakite is an end-member of the hornblende subgroup in the calcic-amphibole group. Calcium-rich amphiboles have the general formula X2-3 Y5 Z8 O22 (OH)2 where X=Ca, NaSodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, K
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
, Mn
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
; Y=Mg, Fe+2 ,Fe+3, Al, Ti
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
, Mn, Cr
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
, Li
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
, Zn
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...
; Z=Si, Al (Deer et al., 1963). The structure of 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...
(Ca2Mg5(Si8O22)(OH,F
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
)2), another calcic amphibole, is commonly used as the standard for calcic amphiboles from which the formulae for their substitutions are derived. The wide range in variety of minerals classified in the amphibole group is due to its great ability for ionic replacement resulting in a widely varying chemical composition. Amphiboles can be classified on the basis of the substitution of ions on the X site as well as the substitution of AlAl for Si(Mg, Fe+2). In the calcium amphiboles like tschermakite Ca2(Mg, Fe2+)3Al2 (Si6 Al2) O22(OH)2, the predominant ion in the X position is occupied by Ca as in tremolite, while the substitution MgSi<->AlAl occurs on the Y and the tetrahedral Z site.
Geologic occurrence
Hornblendes are the most common of the amphiboles and are formed in a wide range of Pressure-Temperature environments. Tschermakite is found in eclogiteEclogite
Eclogite is a mafic metamorphic rock. Eclogite is of special interest for at least two reasons. First, it forms at pressures greater than those typical of the crust of the Earth...
s and ultramafic igneous rock
Igneous 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...
s as well as in medium to high-grade metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
s. The mineral is widespread throughout the world but has most notably been studied in Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, and the Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
(Anthony, 1995). Because amphibole minerals like Tschermakite are hydrous (contain an OH group), they can break down to denser anhydrous minerals like pyroxene
Pyroxene
The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems...
or garnet
Garnet
The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...
at high temperatures. Conversely, amphiboles can be recomposed from pyroxenes as a result of crystallizing igneous rocks as well as during metamorphism (Léger and Ferry, 1991). Because of this important quality, P-T conditions have repeatedly been calculated for the crystallization of hornblendes in calc-alkaline magmas (Féménias et al., 2006). In addition to studying tschermakitic content in its natural occurrences, geologists have frequently synthesized this mineral in order to further calculate its place as an endmember hornblende.
Namesake biography
Gustav Tschermak von Seysenegg
Gustav Tschermak von Seysenegg was an Austrian mineralogist.-Biography:He was born 19 April 1836 in Littau, Olomouc District, Moravia and studied at the University of Vienna where he obtained a teaching degree. He studied mineralogy at Heidelberg and Tübingen and obtained a PhD...
(1836-1927) whose mineral textbook Lehrbuch der Mineralogie (orig. pub.1883) was described as the German language equivalent to the works of Edward Salisbury Dana
Edward Salisbury Dana
Edward Salisbury Dana was an American mineralogist and physicist. He made important contributions to the study of minerals, especially in the field of crystallography.-Life and career:...
(Mineralogy 1885).
In 1872 Professor Tschermak founded one of Europe’s oldest geoscience journals Mineralogische Mitteilungen (Deu: Mineralogical Disclosures) or Mineralogy
Mineralogy
Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...
and Petrology
Petrology
Petrology is the branch of geology that studies rocks, and the conditions in which rocks form....
. In the first volume of Min. Mitt., Tschermak established some of the early classifications of the amphibole group in relation to the pyroxene group of minerals (Tschermak 1871), which no doubt led to the formula Ca2Mg3Al4Si6O22(OH)2 being known as the Tschermak molecule, this mineral formula was later assigned the name tschermakite as first proposed by Winchell (1945).
Professor Tschermak spent many years working as curator for the Imperial Mineralogical Cabinet. The Mineralogical Dept. of the Imperial Natural History Museum
Imperial Natural History Museum
The Imperial Natural History Museum or Imperial Royal Natural History Court Museum of Austria-Hungary was created by Emperor Franz Joseph I during an extensive reorganization of the museum collections, from 1851–1876, and opened to the public on August 10, 1889.Located in Vienna, the Museum was...
in Vienna – an impressive mineral, meteorite and fossil collection has Professor Tschermak to thank for his detailed inventory system that has helped preserve it to this day as well as the expansion of their meteorite collection. He was a full professor of mineralogy and petrography at the University of Vienna
University of Vienna
The University of Vienna is a public university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world...
as well as a full member of the Imperial Academy of Sciences in Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
. He was also the first president of the Viennese (now Austrian) Mineralogical Society, founded in 1901.
An obituary for “Hofrat Professor Dr. Gustav Tschermak” written by Edward S. Dana (1927) can be found in the 12th volume of American Mineralogist where Dana recalls the two young scientists earlier work together in the Vienna Mineral Cabinet and remarks on Professor Tschermak’s vigor and clarity of mind maintained up to his final days. Gustav Tschermak’s third child, Erich von Tschermak
Erich von Tschermak
Erich von Tschermak-Seysenegg was an Austrian agronomist who developed several new disease-resistant crops, including wheat-rye and oat hybrids. He was a son of the Moravia-born mineralogist Gustav Tschermak von Seysenegg...
-Seysenegg (1871-1962) was a renowned botanist who is credited for independently resdiscovering Gregor Mendel
Gregor Mendel
Gregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
’s genetic laws of inheritance by working with similar plant breeding experiments.
Mineral structure
The amphibole group consists of an orthorhombic and monoclinic series – hornblendeHornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
s and tschermakite both belong to the latter crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
. The crystal group of tschermakite is 2/m.
Tschermakite and all the hornblende varieties are inosilicates, and like the other rock forming amphiboles are double chain silicates (Klein and Hurlbut, 1985). The amphibole structure is characterized by it’s two double chains of SiO4 tetrahedra (T1 and T2) sandwiching in a strip of cations (M1, M2 and M3 octahedra). Much of the discussions and studies of both tschermakite and tremolite have been to resolve the varying cation placements and Al substitutions that seem to occur on all T and M sites (Najorka and Gottschalk, 2003).
Physical properties
A hand specimen of tschermakite is green to black in color; its streak will be greenish white. It can be transparent to translucent and has a vitreous luster. Tschermakite shows the characteristic amphibole perfect cleavage on [110]. Its average density is 3.24, with a hardness of 5-6; its fractureFracture
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...
will be brittle to conchoidal. In thin section
Thin section
In optical mineralogy and petrography, a thin section is a laboratory preparation of a rock, mineral, soil, pottery, bones, or even metal sample for use with a polarizing petrographic microscope, electron microscope and electron microprobe. A thin sliver of rock is cut from the sample with a...
its optic sign and 2V angle cover a wide range and are not very useful for identification. It shows a distinct pleochroism
Pleochroism
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles with polarized light.- Background :Anisotropic crystals will have optical properties that vary with the direction of light...
in browns and greens.