Amphibole

  • Hornblende

The amphibole (short: amphiboles ) includes silicates, structurally characterized by double chains of corner-sharing SiO4 tetrahedra and complying with the composition of the following generalized empirical formula:

A0 1B2C5T8O22 (OH ) 2

In this structure formula, the capital letters A, B, C and T represent different positions in the Amphibolstruktur. They are confirmed by the following cations:

  • A: vacancies, Na , K , Ba2 , Sr2 , Ca2 , Li
  • B: Ca2 , Na , Mg2 , Fe2 , Mn2 , Li , Sr2 , Ba2 , Mn2 , Fe2 , Co2 , Ni2 , Zn2 , Mg2 , Pb2 , Cu, Zr, Mn3 , Cr3 , V, Fe 3 ,
  • C: Mg2 , Fe2 , Mn2 , Li , Al3 , Zn2 , Ni2 , Co2 , Ti4 , Fe3 , V, Cr3 , Mn3 , Zr,
  • T: Si4 , Al3 , Ti4

Instead of the hydroxyl group (OH ) contain amphiboles and F-, Cl -, O2 -

Highlighted in bold are the dominant cations are on the individual items.

Amphiboles are the mineral group with probably the largest chemical variability. Not least because amphiboles occur worldwide in many different paragenesis and geological environment. They are an important part of both igneous as well as metamorphic rocks of different composition and formation conditions.

  • 2.1 silicate anion
  • 2.2 Coordination of the divalent and trivalent cations,
  • 2.3 I- Beams

Classification and Nomenclature

Due to the chemical and structural complexity of the amphiboles, the creation of a globally recognized nomenclature for decades has attracted. But the elaboration of the first proposal of the International Mineralogical Association (IMA ) ( 1978) pulled down 13 years. It took nine more years to simplify this proposal and adapt to new discoveries. This 1997 presented Amphibolnomenklatur was revised again until 2003 and extended by a further amphibole.

Based on a correct designation of amphibole is a complete chemical analysis and the application of a predetermined calculation scheme that normalizes the exact contents of the individual elements and the individual positions (A, B, C, T) be split.

With the occupation of the B- position, the amphiboles are then divided into five groups:

In these five groups of 78 base name for amphiboles are set. Deviations of the mentioned following compositions, for example, by the incorporation of other non-specified herein cations in the crystal lattice, such as chromium, lead, potassium ... is carried by name prefixes and adjectives preceding statement.

Prefixes in Amphibolnamen

Prefixes indicate significant substitutions and are an integral part of the name. You will be the base name prefixed directly, in the same word or separated by a hyphen.

First some adjectives to describe minor variations of the compositions. They are preceded by an adjective without a hyphen as a base name ( bariumhaltig, boracic, leaded, Nickelhaltig, ...).

In the structural formulas given below in brackets, the atoms can be represented in any combination by substitution, but always stand in the same relation to the other groups of atoms.

Magnesium - iron - manganese -lithium amphiboles

Amphiboles of this group occur in both orthorhombic and monoclinic symmetry.

Orthorhombic amphiboles:

Most orthorhombic amphiboles crystallize in the space group Pnma. The occurrence of the space group Pnmn can be characterized by the prefix proto behalf.

Anthophyllite series:

This series includes the amphibole composition NaxLiz ( Fe2 , Mg, Mn) 7 -y- ZALY ( Si8 -x -y zAlx yz) O22 (OH, F, Cl ) 2 with Si > 7.0 and Li < 1, 0 The following end-members form the boundaries of the Anthophyllitzusammensetzungen:

  • Anthophyllite Mg7Si8O22 (OH) 2
  • Ferro - anthophyllite Fe7Si8O22 (OH) 2
  • Natriumanthophyllit NaMg7Si7AlO22 (OH) 2
  • Sodium - ferro - anthophyllite NaFe7Si7AlO22 (OH) 2

Gedrite series:

Compositions of this range can be described by the same structural formula as the anthophyllite series, but with Si <7.0. The series contains the following end members:

  • Ferrogedrit Fe5Al2 ( Si6Al2 ) O22 (OH) 2
  • Gedrite Mg5Al2 ( Si6Al2 ) O22 (OH) 2
  • Sodium Ferrogedrit NaFe6Al ( Si6Al2O22 ) (OH) 2
  • Natriumgedrit NaMg6Al ( Si6Al2 ) O22 (OH) 2

Holmquistit series:

This series contains amphiboles of composition [ Li2 ( Fe2 , Mg ) 3 ( Fe 3 , Al) 2] Si8O22 (OH, F, Cl ) 2, Li > 1.0.

  • Holmquistit ( Li2Mg3Al2 ) Si8O22 (OH) 2
  • Ferroholmquistit ( Li2Fe3Al2 ) Si8O22 (OH) 2

Monoclinic amphiboles

Cummingtonite - grunerite series:

Amphibole this series to the general formula (Mg, Fe, Mn, Li) 7Si8O22 (OH) 2 Li < 1.0.

  • Cummingtonite Mg7Si8O22 (OH) 2
  • Grunerite Fe7Si8O22 (OH) 2
  • Manganocummingtonit Mn2Mg5Si8O22 (OH) 2
  • Manganogrunerit Mn2Fe5Si8O22 (OH) 2
  • Permanganogrunerit Mn4Fe3Si8O22 (OH) 2

Klinoholmquistit series:

This series is represented by the structural formula [ Li2 ( Fe2 , Mg, Mn ) 3 ( Fe3 , Al) 2] Si8O22 (OH, F, Cl ) 2 described with more than 1.0 Li at the B- position and, decisively, less 0.5 Li to the C position.

  • Klinoferroholmquistit ( Li2Fe3Al2 ) Si8O22 (OH) 2
  • Klinoholmquistit ( Li2Mg3Al2 ) Si8O22 (OH) 2
  • Ferri - Klinoferroholmquistit ( Li2Fe2 3 Fe3 2) Si8O22 (OH) 2
  • Ferri - Klinoholmquistit ( Li2Mg2 3 Fe3 2) Si8O22 (OH) 2

Pedrizit - Ferropedrizit series:

This series is represented by the structural formula NaLi2 [Li ( Fe2 , Mg, Mn ) 2 ( Fe3 , Al) 2] Si8O22 (OH, F, Cl ) 2 described with more than 1.0 Li at the B- position and, decisively, Li greater than 0.5 on the C position.

  • Sodium Pedrizit: NaLi2 ( LiMg2 2 Fe3 Al ) Si8O22 (OH) 2
  • Sodium Ferropedrizit: NaLi2 ( Life2 2 Fe3 Al ) Si8O22 (OH) 2

Calcium amphiboles

This group, often synonymously referred to as hornblende, comprising of monoclinic amphiboles with more than 1.5 Ca at the B position. A further subdivision can be made based on the occupation of the A- position. This group includes the following end members:

Calcium amphiboles with less than 0.5 (Na, K ) on the A- position:

  • Ca2Mg5Si8O22 tremolite (OH) 2
  • Ferro - actinolite Ca2Fe2 5 Si8O22 (OH) 2
  • Magnesiohornblende Ca2 [ Mg4 (Al, Fe 3 )] ( Si7Al ) O22 (OH, F) 2
  • Ferrohornblende Ca2 [Fe2 4 (Al, Fe 3 )] ( Si7Al ) O22 (OH, F) 2
  • Tschermakite Ca2 ( Mg3Fe3 Al ) ( Si6Al2 ) O22 (OH) 2
  • Ferrotschermakit Ca2 ( Fe2 3 Fe3 Al ) ( Si6Al2 ) O22 (OH) 2
  • Aluminotschermakit Ca2 ( Mg3Al2 ) ( Si6Al2 ) O22 (OH) 2
  • Alumino- Ferrotschermakit Ca2 ( Fe2 3 Al2 ) ( Si6Al2 ) O22 (OH) 2
  • Ferritschermakit Ca2 ( Mg3Fe3 2) ( Si6Al2 ) O22 (OH) 2
  • Ferri - Ferrotschermakit Ca2 ( Fe2 3 Fe3 2) ( Si6Al2 ) O22 (OH) 2

Calcium amphiboles with more than 0.50 Ca on the A- position:

  • Cannilloit CaCl 2 ( Mg4Al ) ( Si5Al3 ) O22 (OH) 2

Calcium amphiboles with more than 0.5 (Na, K ) on the A- position:

  • Edenit NaCa2Mg5 ( Si7Al ) O22 (OH) 2
  • Ferromagnetic Edenit NaCa2Fe2 5 ( Si7Al ) O22 (OH) 2
  • Pargasite NaCa2Mg4Al ( Si6Al2 ) O22 (OH) 2
  • Ferro - pargasite NaCa2Fe2 4 Al ( Si6Al2 ) O22 (OH) 2
  • Magnesiohastingsit NaCa2Mg4Fe3 ( Si6Al2 ) O22 (OH) 2
  • Hastingsite NaCa2Fe2 4 Fe3 ( Si6Al2 ) O22 (OH) 2
  • Magnesiosadanagait NaCa2 [ Mg 3 ( Fe3 , Al ) 2] ( Si5Al3 ) O22 (OH) 2
  • Sadanagait NaCa2 [Fe2 3 ( Fe3 , Al ) 2] ( Si5Al3 ) O22 (OH) 2

Calcium amphiboles with more than 0.5 (Na, K ) on the A- position and more than 0.50 Ti:

  • Kaersutite NaCa2 ( Mg4Ti ) ( Si6Al2 ) O22 (OH) 2
  • Ferrokaersutit NaCa2 ( Fe2 4 Ti) ( Si6Al2 ) O22 (OH) 2

Sodium -calcium amphiboles

This group includes monoclinic amphiboles with more than one (Ca, Na ) on the B point (B (Ca, Na) > = 1.0), and Na contents on the B - position 0.50 to 1.50 apfu (atoms per formula unit ). A further subdivision is based on the occupation of the A- position. The following end-members also belong to this group:

Sodium -calcium amphiboles with more than 0.50 (Na, K ) on the A- position ( richterite - Katophorit - Taramit ):

  • Richterite Na ( CaNa ) Mg5Si8O22 (OH) 2
  • Ferrorichterit Na ( CaNa ) Fe2 5 Si8O22 (OH) 2
  • Magnesiokatophorit Na ( CaNa ) ( Mg4 (Al, Fe3 )) ( Si7Al ) O22 (OH) 2
  • Katophorit Na ( CaNa ) ( Fe2 4 (Al, Fe3 )) ( Si7Al ) O22 (OH) 2
  • Magnesiotaramit Na ( CaNa ) ( Mg3AlFe3 ) Si6Al2O22 (OH) 2
  • Taramit Na ( CaNa ) ( Fe2 3 AlFe3 ) Si6Al2O22 (OH) 2
  • Potassium Aluminotaramit K ( CaNa ) ( Fe2 3 Al2 ) Si6Al2O22 (OH) 2

Sodium -calcium amphiboles with less than 0.50 (Na, K ) on the A- position ( Winchit - Barroisite ):

  • Winchit ( CaNa ) Mg4 (Al, Fe3 ) Si8O22 (OH) 2
  • Ferrowinchit ( CaNa ) Fe2 4 (Al, Fe3 ) Si8O22 (OH) 2
  • Barroisite ( CaNa ) ( Mg3AlFe3 ) ( Si7Al ) O22 (OH) 2
  • Ferrobarroisit ( CaNa ) ( Fe2 3 AlFe3 ) ( Si7Al ) O22 (OH) 2
  • Aluminobarroisit ( CaNa ) ( Mg3Al2 ) ( Si7Al ) O22 (OH) 2
  • Alumino- Ferrobarroisit ( CaNa ) ( Fe2 3 Al2 ) ( Si7Al ) O22 (OH) 2
  • Ferribarroisit ( NaCa ) ( Mg3Fe3 2) Si7AlO22 (OH) 2
  • Ferri - Ferrobarroisit ( CaNa ) ( Fe2 3 Fe3 2) ( Si7Al ) O22 (OH) 2

Alkali amphiboles

This group includes monoclinic amphiboles with more than 1.50 Na at the B position. This group is divided on the basis of Li and Mn contents and the Na contents on the A- position.

Alkali amphiboles with less than 0.5 Li ( Mn2 Mn3 ) <( Vial Fe3 Fe2 Mg) and less than 0.50 Na K on the A- position: glaucophane, Riebekit

  • Glaucophane Na2 ( Mg3Al2 ) Si8O22 (OH) 2
  • Ferroglaukophan Na2 ( Fe2 3 Al2 ) Si8O22 (OH) 2
  • Magnesioriebeckite Na2 ( Mg3Fe3 2) Si8O22 (OH) 2
  • Riebeckite Na2 ( Fe2 3 Fe3 2) Si8O22 (OH) 2

Alkali amphiboles with less than 0.5 Li ( Mn2 Mn3 ) <( Vial Fe3 Fe2 Mg) and more than 0.50 Na K on the A- position: Eckermannit, Arfvedsonite, Obertiit, Nyböit

  • Eckermannit NaNa2 ( Mg4Al ) Si8O22 (OH) 2
  • Ferromagnetic Eckermannit Na3 ( Fe 2 Al 4 ) Si8O22 (OH) 2
  • Magnesio - Arfvedsonite NaNa2 ( Mg4Fe3 ) Si8O22 (OH) 2
  • Arfvedsonite NaNa2 ( Fe2 4 Fe3 ) Si8O22 (OH) 2
  • Obertiit NaNa2 ( Mg3Fe3 Ti) 2Si8O22O2
  • Nybøit NaNa2Mg3Al2 ( Si7Al ) O22 (OH) 2
  • Ferronybøit NaNa2 ( Fe2 3 Al2 ) ( Si7Al ) O22 (OH) 2
  • Ferrinybøit NaNa2 ( Mg3Fe3 2) ( Si7Al ) O22 (OH) 2
  • Ferri - Ferronybøit NaNa2 ( Fe2 3 Fe3 2) ( Si7Al ) O22 (OH) 2

Alkali amphiboles with less than 0.5 Li ( Mn2 Mn3 )> ( Vial Fe3 Fe2 Mg) and more than 0.50 Na K on the A- position: Ungarettiit, Kozulit

  • Ungarettiit NaNa2 ( Mn2 Mn3 3 2 Si8O22 (OH ) 2)
  • Kozulith Na3 ( Mn2 4 ( Fe3 , Al) ) Si8O22 (OH) 2

Alkali amphiboles with more than 0.5 Li: Leakeit, Kornit

  • Leakeit NaNa2 ( Mg2Fe3 2 Li) Si8O22 (OH) 2
  • Ferroleakeit NaNa2 ( Fe2 2 Fe3 2 Li) Si8O22 (OH) 2
  • Kornit (Na, K) Na2 ( Mg2Mn3 2 Li) Si8O22 (OH) 2

Sodium - calcium - magnesium - iron - manganese -lithium amphiboles

This group was introduced by the IMA until 2003 to be more recent finds of amphiboles with unusually high levels of small divalent cations (Mg, Mn, Fe, ... ) needs. Characteristic of amphiboles of this group is a cast of the B- position with 0.50 < (Mg, Fe2 , Mn2 , Li) < 1.50 and 0.50 ≤ (Na, Ca) ≤ 1.50.

Group5 - amphiboles with more than 0.50 Li at the B- position

  • Ottoliniit ( NaLi ) ( Mg3Fe3 Al ) Si8O22 (OH) 2
  • Ferri - Ottoliniit: ( NaLi ) ( Fe2 3 Fe3 Al ) Si8O22 (OH) 2
  • Whittackerit: Na ( NaLi ) ( LiMg2Fe3 Al ) Si8O22 (OH) 2
  • Ferriwhittackerit: Na ( NaLi ) ( Life2 2 Fe3 Al ) Si8O22 (OH) 2

Group5 - amphiboles with less than 0.50 Li at the B- position

Here are the names of groups 1 to 4 are used, supplemented with the prefix parvo ' (Latin for, small' ) to refer to the increased levels of small cations on the B position.

Structure

The wide variation in the chemical composition of the amphiboles is explained by their structure. It has the cation positions of very different size and shape, providing a variety of cations of different size and charge space. In all these cation positions, the cations are surrounded by oxygen anions when going from smaller fluorine contents apart again. The different positions are different in the number of the surrounding anions ( coordination number ), the distance to the cation and arrangement around the cation. Generally speaking, the more a cation surrounded anions, the larger the average distance from the cation to the anion position, the weaker the individual bonds and the greater the ionic character of the bonds.

The Amphibolstruktur has cation positions with 4 different coordination numbers.

  • Tetrahedral positions: 4 anions surrounding a cation tetrahedron- shaped. This position offers small cations with high charge mostly space ( Si4 , Ti4 , Al3 ). The short cation-anion bonds have a high covalent ratio (atomic bonds). Atomic bonds are highly directional. Therefore, the geometry of the atomic orbitals must be as good as possible binding in accordance with the arrangement of the surrounding anions.
  • Octahedral: six anions surrounding a cation octahedron. This position offers medium-sized, mostly di-and trivalent cations space ( Mg2 , Fe2 , Mn2 , Al3 , Fe3 ). The bonds are primarily non-directional ionic.
  • 8-fold coordinated places: 8 anions surrounding a cation in the form of a cubic antiprism. This position offers great one to divalent cations space (Na , Ca2 ). The bonds are weak and ionic.
  • 12-fold coordinated sites: This position offers a very large one to divalent cations space (Na , K ). The bonds are very weak ionic.

The structure diagrams show the sake of clarity only the faces of these polyhedra. The oxygens and cations themselves are not shown. The oxygen anions are located on the corners of the polyhedron, the cations in the center of the polyhedron.

Silicate anion

The structural characteristic of all amphiboles is the double chain of SiO4 tetrahedra with the empirical formula [ Si4O11 ] 6 -. After the silicate classification of F. Liebau the amphiboles belonging to the group of unbranched two double-chain silicates.

Silicon is surrounded by four oxygen atoms, which form the corners of a tetrahedron in the center of the Si4 cation located. This SiO 4 -tert Raeder are two oxygens connected to ideally infinite chains. Two such chains are connected via every other SiO4 tetrahedra to form double chains ( see figure).

This results in two structurally different SiO4 tetrahedra. The tetrahedron T1 connects the two twin single chains to a two - double chain and is about three oxygens connected to adjacent SiO4 tetrahedra. The tetrahedron T2 is connected only via two oxygens with neighboring SiO4 tetrahedra.

The SiO4 tetrahedra are arranged in the double chains so that they all show a tetrahedron point in the same direction approximately perpendicular to the double chain plane. Accordingly, all tetrahedron with a face in the opposite direction. The figure shows a section of a SiO4 two double chain with a view of the tetrahedra base surfaces.

Coordination of the divalent and trivalent cations,

The C-position of the structural formula above includes the three structurally distinct positions M1, M2 and M3. On these three positions, the smaller cations (mainly Mg2 , Fe2 , Mn2 , Al3 ) are octahedrally coordinated by six oxygens.

The octahedron of C position are linked via common Did to ideally infinite Oktaederbändern. The B position is located at the edges of Oktaederbänder and establishes the connection to adjacent SiO4 tetrahedra double chains.

The B- position (in structural descriptions usually referred to as M4 - position) is surrounded by eight oxygens that lie on the vertices of a distorted cubic or tetragonal antiprism. This position offers room for larger divalent cations such as Ca or Pb (all Calciumamphibole, such as tremolite ), but can also be fully occupied by Mg and Fe (eg, anthophyllite, grunerite ).

The A-site is surrounded by 12 oxygens. It lies between two silicate double chains approximately above or below the center of SiO4 six-membered rings (see figure), thus providing a weak link of the I - beams (see next section ) with one another here. The double chains are superimposed not exactly so that there is a very irregular oxygen configuration for the A position.

I- Beams

The two tetrahedral double chains are connected via their free tips with the top or bottom of a Oktaederbandes. This sandwich -like assembly is also referred to as I-beam because of their resembling the capital letters I cross-section.

These I- beams are connected to each other via the M4 and M2 octahedron, wherein the edges of the silicate double chains are bonded to the octahedron M4 and M2 of the adjacent I- beams.

Education and Locations

The iron-rich hornblende, a particularly important amphibole, which contains iron high levels of calcium, sodium and magnesium, both in igneous, and metamorphic rocks in such as amphibolite occurs. Tremolite, actinolite or nephrite, the latter as the main part of Jade, found primarily in metamorphic rocks.

Locations are there worldwide, therefore the above-mentioned list of the sites can not be complete:

Green Bushes / Western Australia in Australia, Brumado / Bahia in Brazil, ground corn in Germany, Quebec in Canada, Manono in the DRC, fire bridges in Austria, Snarum and Uto in Sweden, Campolungo in Switzerland, Hermanov in the Czech Republic, Dnipropetrovsk Oblast in Ukraine, New York in the United States.

Use

Until the 1970s, among others, riebeckite ( crocidolite, blue asbestos ) was less robust and processed refractory insulation and tissues.

Heinrich Harrer reported at the crossing of West Papua in 1962 that they'd use the Dani in the area around Mulia next to the green epidote and glaucophane blue for the production of stone axes. At selected points in the quarry fires were kindled and canceled hours later with boulders, rock wedges and bars and brought to safety with wooden tongs. Harrer amazed how quickly axed the stones and the raw form of the stone ax is revealed.

Precautions

Actinolite, anthophyllite, riebeckite and tremolite from the amphibole asbestos, like all known to cause lung diseases such as asbestosis or mesothelioma.

Chemical formula Color Streak (mineralogy) Cleavage (crystal) Crystal habit Bodenmais Manono Island Heřmanov (Děčín District) List of minerals Paul Ramdohr Karl Hugo Strunz
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