Axinite
Axinit (also Thumerstein or Thumit ) is the collective name for a group of unspecified minerals from the mineral class of " silicates and Germanates ". It is the end members of a solid solution with the following composition:
- Axinit - (Fe) (formerly Ferro - Axinit ): Ca2Fe2 Al2B [O | OH | ( Si2O7 ) 2]
- Axinit - (Mg ) ( magnesio - Axinit ) Ca2MgAl2B [O | OH | ( Si2O7 ) 2]
- Axinit - (Mn ) ( Manganaxinit ) Ca2Mn2 Al2B [O | OH | ( Si2O7 ) 2]
As an intermediate member yet one tinzenite with the composition ( Ca, Mn 2 ) 2 ( Mn2 , Fe2 ) Al2B [O | OH | ( Si2O7 ) 2] to this mineral series.
Special Features
Some manga -rich samples exhibit red luminescence.
Etymology and history
Axinit was first described by the French mineralogist René -Just Haiiy 1797, who named the mineral after his often characteristic, ax or beilähnlichen crystal form ( ancient Greek ἀξίνη axíne ).
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz among the minerals of the Axinit group with the system no. VIII/C.08 to the Department of " group silicates ( Sorosilikate ) ".
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Mineral classification Strunz'schen the Axinit group also arranges in the department of " group silicates ( Sorosilikate ) " a. However, this is further divided according to the structure of the silicate groups, so that the specific genre in the group minerals according to their construction in the subdivision " Si2O7 groups with additional anions; Cations are located in tetrahedral and / or other co-ordination ". The Axinit group wears the system no. 9.BD.20.
The mainly common in English-speaking classification of minerals according to Dana assigns the Axinit group in the department of " group silicates ". Here she is with the system no. ": With cations and / or Si2O7 Groups and O, OH, F, and H2O > Coordination Group silicates " to find 56.02.02 within the subdivision.
Education and Locations
Axinite formed mainly by hydrothermal processes and by contact metamorphism in Alpine fissures and calcareous rocks. Accompanying minerals occur among others actinolite, albite, andradite, calcite, chlorite, Datolith, epidote, hedenbergite, clinozoisite, prehnite, quartz, tremolite, tourmaline, vesuvianite and zoisite.
Axinit generally comes rarely occurs, that is, it can still be abundant in part to different sites, overall it is not very common. Are the most common Axinit - (Fe) with approximately 230 known archaeological sites, followed by Axinit - (Mn ), with approximately 60 and Axinit - (Mg) with about 10 known localities (as of 2012).
In Germany came Axinit - (Fe) and Axinit - (Mn ) has so far only in the resin ( Bad Harzburg, Treseburg ), wherein the resin for the Axinit - (Mn ) is considered the type locality. In addition, it was previously found in the area around Thum in Saxony's Ore Mountains, hence the name Thumerstein or Thumit stirred.
In Austria, however, was Axinit - (Fe) in several places in Carinthia ( Koralpe Saualpe ) and Salzburg ( Hohe Tauern, Saalfelden ), Axinit - (Mg) previously only Schwallenbach in Lower Austria.
In Switzerland Axinit - (Fe) could be detected among others Steinibach ( Elm, Glarus ) and at several locations in the cantons of Graubünden, Ticino, Uri and Wallis.
Other localities lie including Australia, Chile, China, Finland, France, Iran, Ireland, Italy, Japan, Kazakhstan, Madagascar, Mexico, Morocco, Namibia, New Zealand, Norway, Pakistan, Peru, Poland, Romania, Russia, Sweden, Slovakia, Spain, South Africa, Tanzania, Czech Republic, Turkey, Hungary, the United Kingdom ( UK) and the United States of America (USA).
Axinit - (Fe) from New Melones Dam, Calaveras County, California, USA (size: 5.3 x 5 x 0.6 cm)
Axinit - (Mg) from Merelani Hills ( Mererani ) Lelatema Mountains, Arusha, Tanzania ( Size: 2.1 x 1.5 x 0.5 cm)
Axinit - (Mn ) from Dalnegorsk, Primorye, Russia ( Size: 4.1 x 4 x 3.8 cm)
Axinit - (Mn ) of Vitória da Conquista, Bahia, Brazil ( Size: 5.5 x 2.4 x 0.8 cm)
Crystal structure
All minerals of Axinit group crystallize in the triclinic space group P1 ( Raumgruppen-Nr. 2), but differ due to the slightly different ionic radii of iron (82 pm ), magnesium ( 91 pm ) and manganese (78 pm ) in the lattice parameters:
- Axinit - (Fe): a = 7.16 Å; b = 9.20 Å; c = 8.96 Å; α = 91.8 °; β = 98.1 ° and γ = 77.3 °
- Axinit - (Mg): a = 7.14 Å; b = 9.16 Å; c = 8.94 Å; α = 91.9 °; β = 98.1 ° and γ = 77.5 °
- Axinit - (Mn ): a = 7.16 Å; b = 9.18 Å; c = 8.96 Å; α = 92.0 °; β = 98.3 ° and γ = 77.3 °
The number of formula units per unit cell is two.
Axinite the structure can be used as a sequence of borosilicate tetrahedral layers and layers of octahedrally coordinated cations (Al, Fe, Ca, Mn, Mg) will be described.
Silicon (Si) and boron ( B) are tetrahedrally coordinated by four oxygens (O) surrounded. Each two SiO4 tetrahedra are connected via a common corner to a Si2O7 group. Four such Si2O7 groups linked by two BO4 Teraeder shared corners to a 6 Borosilikatring branch off two Si2O7 groups of the. These branched borosilicate anion complexes are (2 1 1 ) plane is arranged in layers parallel to.
Aluminum (Al ), iron ( Fe), and calcium (Ca) are octahedrally surrounded by six oxygen atoms. Four AlO6 octahedra are connected via common edges to form a chain at each end of which a FeO6 octahedra sits. These linear 6- Oktaedergruppen are connected via highly distorted octahedra CaO6 to layers.
Use
Is Axinit because of its often pronounced crystals in Axtform primarily a collector's mineral. With good quality but it will occasionally also made into gemstones.