Staněkit

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Staněkit
General and classification
other names
  • Mineral OKAA
  • IMA 1994-045
  • Staněkit- Ma2bc
  • Stanekit
chemical formula
  • Fe 3+ (Mn, Fe 2+ , Mg) (PO 4 ) O
  • (Mn 2+ , Fe 2+ , Mg) Fe 3+ (PO 4 ) O
  • Fe 3+ Mn 2+ O (PO 4 )
  • (Mn, Fe 2+ , Mg) Fe 3+ [O | PO 4 ]
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.BB.15 ( 8th edition : VII / B.03)
06/41/03/06
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / a (No. 14, position 3)Template: room group / 14.3
Lattice parameters a  = 11.844  Å ; b  = 12.662 Å; c  = 9.983 Å
β  = 105.93 °
Formula units Z  = 16
Twinning none observed
Physical Properties
Mohs hardness 4 to 5
Density (g / cm 3 ) 3.80 (measured); 4.09 (calculated)
Cleavage none observed
Break ; Tenacity splintery; brittle
colour black
Line color dark brown
transparency opaque, only translucent in thin splinters
shine weak semi-metallic luster
Crystal optics
Refractive indices n α  = 2.010
n β  = 2.110
Birefringence δ = 2.010
Optical character biaxial

Staněkit is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition Fe 3+ (Mn, Fe 2+ , Mg) (PO 4 ) O and is therefore chemically a manganese - iron - phosphate with an additional oxygen atom , i.e. an oxophosphate.

At its type locality, Staněkit only develops xenomorphic grains up to 2 cm long, stretched along the c-axis [001], which come together to form subparallel aggregates and are accompanied by ferrisicklerite , heterosite , kryzhanovskite , arrojadite , eosphorite and " alluaudite in the broader sense". Common type localities for the mineral are the rare metal granite pegmatite Clementine II on the farm Okatjimukuju 55 (Farm Friedrichsfelde) near Karibib , constituency Karibib in the Erongo region , Namibia , and the Albères massif , eastern Pyrenees , Occitania , France .

Etymology and history

Staněkite was found by Paul Keller and Oleg von Knorring in the late 1980s during investigations into phosphate minerals in pegmatites at the Okatjimukuju 55 farm, which mineral was characterized as easily confusing with ferrisicklerite, sicklerite and / or kryzhanovskite. After a phase found in the intrusion of Albères in the French Pyrenees had proven to be identical to the mineral from the pegmatite Clementine II, Paul Keller, Professor of Mineralogy and Crystallography at the University of Stuttgart , together with colleagues carried out a characterization as new Mineral necessary examinations. The results were presented to the International Mineralogical Association (IMA), which approved it on December 30, 1994 under the temporary designation IMA 1994-045. In 1997 it was described by Paul Keller, François Fontan , Francisco Velasco Roldan and Joan Carles Melgareji i Draper in the German science magazine "European Journal of Mineralogy" as Staněkit ( English Staněkite ). The authors named the mineral after Josef Staněk from the Department of Geological Sciences at Masaryk University in Brno , Moravia , Czech Republic , a specialist in the mineralogy of phosphates who has intensively studied Moravian pegmatites.

The type material for Staněkit (parts of the holotype) is kept at the University of Stuttgart (location TM-94.45-OKAA / 0/824-s27 / 2). Further type material was obtained from Mines ParisTech (until 2008 École des mines de Paris, Mines Paris ), France , under the collection no. T45634, deposited.

classification

Already in the outdated, but still in use 8th edition of the mineral classification according to Strunz , the Staněkit belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the division of "anhydrous phosphates, with foreign anions F, Cl, O, OH", where together with Zwieselit and Wolfeit the "Zwieselit-Wolfeit-Gruppe" with the system no. VII / B.03 and the other members Magniotriplit (discredited 2004), Sarkinit , Triplit , Triploidit and Wagnerit formed.

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns the Staněkit to the category of “Phosphates etc. with additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions to the phosphate, arsenate and vanadate complex, so that the mineral is classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4  ≤ 1: 1 “can be found where, together with Joosteit , Sarkinit, Triploidit, Wagnerite and Wolfeit, the“ Triploiditgruppe ”with the system no. 8.BB.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Staněkit to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is together with Wolfeit, Triploidit, Sarkinit and Joosteit in the " Wolfeit group " with the system no. 41.06.03 within the subsection "Anhydrous phosphates etc., with hydroxyl or halogen with (A) 2 (XO 4 ) Z q ".

Chemism

Microprobe analyzes on countless staněkite grains from the "Clementine II pegmatite" resulted in mean values ​​of 0.13% Na 2 O; 0.05% K 2 O; 0.50% MgO; 0.13% CaO; 23.12% MnO; 1.56% FeO; 0.22% ZnO; 0.01% Al 2 O 3 ; 41.56% Fe 2 O 3 (FeO / Fe 2 O 3 ratio calculated according to the values ​​from Mössbauer spectroscopy ); 0.02% TiO 2 and 31.16% P 2 O 5 . On the basis of five oxygen atoms , the empirical formula was calculated from them (Fe 3+ 1.16 Mn 2+ 0.73 Fe 2+ 0.05 Mg 0.03 Na 0.01 ) Σ = 1.98 (P 0, 98 O 4 ) O, which was idealized to Fe 3+ (Mn, Fe 2+ , Mg) (PO 4 ) O. This ideal formula with Mn: Fe: Mg = 0.77: 0.20: 0.063 requires contents of 0.55% MgO; 24.71% MnO; 6.65% FeO; 36.12% Fe 2 O 3 and 32.11% P 2 O 5 (total 100.00 wt%).

Staněkit (more precisely Staněkit- Mabc ) is the Fe 3+ -dominant analogue of the Mn 3+ -dominated joosteite .

Crystal structure

Staněkite crystallizes in the monoclinic crystal system in the space group P 2 1 / a (space group no. 14, position 3) with the lattice parameters a  = 11.844  Å ; b  = 12.662 Å; c  = 9.983 Å and β = 105.93 ° and 16 formula units per unit cell. This is one of two known monoclinic polytypes of Staněkit - the polytype Staněkit-Ma2bc . Template: room group / 14.3

The other polytype Staněkit-Mabc also crystallizes monoclinically in the space group I 2 / a (space group no. 15, position 3) with the lattice parameters a  = 11.835  Å ; b  = 6.328 Å; c  = 9.984 Å and β = 105.81 ° as well as eight formula units per unit cell . Template: room group / 15.3

The crystal structure of Staněkit consists of an almost undistorted [PO 4 ] tetrahedron and two symmetrically different, strongly distorted [MO 6 ] octahedra . The cations M are distributed in both octahedral positions regardless of their valence . The [MO 6 ] octahedra have common edges and form zigzag chains that run parallel [010] for [(M1) O 6 ] and [100] for [(M2) O 6 ]. Both types of chains are linked by further edges along the c-axis and thereby form an open framework in which the isolated [PO 4 ] tetrahedra are located. Staněkit and synthetic α- and β-Fe 2 [PO 4 ] O are polymorphs . In contrast to Staněkit, the synthetic polymorphs are characterized by [MO 6 ] octahedra with common faces, which are linked together by straight or tightly folded zigzag chains for both β-Fe 2 [PO 4 ] OI and β-Fe 2 [PO 4 ] O-II and α-Fe 2 [PO 4 ] O are connected.

The crystal structures of both Staněkit-Mabc and Staněkit-Ma2bc differ significantly in the coordination numbers of their cations and anions, such as B. Wolfeit- Ma2bc , (Fe, Mn, Mg,) 2 [PO 4 ] (OH). For the latter minerals half of the cations are either five- or six-fold coordinated and the coordination number of the isolated anions (CN OH ) is only three, while in the Staněkit all cations are six-fold coordinated and the single oxygen atom O5, which does not belong to any [PO 4 ] 3– tetrahedron, has CN O5  = 4.

Staněkit- mAbC is isotypic (isostructural) to its Mn 3+ analogue Joosteit.

properties

Drawing of an idealized staněkite crystal. The purple withstanding areas are not end surfaces, but rather due to the good divisibility of the mineral at right angles to [001].

morphology

Staněkite occurs at its type locality in the "Clementine II pegmatite" in the form of 0.2 to 5 mm large, xenomorphic grains, which in most cases are stretched in the direction of the c-axis [001] and grown parallel to and on it Form aggregates up to 2 cm in size. Indistinct surfaces of the prism {120} have developed on some crystals (compare the crystal drawing opposite). There also seem to be flat shapes that form the terminations in the head area of ​​the crystals, but these are exclusively due to the good divisibility of the Staněkit. In most cases the crystal fragments of the Staněkit are composed of both polytypes (both Staněkit-Mabc and Staněkit-Ma2bc with the double b-axis) in different proportions.

physical and chemical properties

The aggregates of the Staněkit are black, their line color is always dark brown. The surfaces of the opaque aggregates, which only show through in thin splinters, have a weak semi-metallic sheen , which agrees well with the values ​​for the refraction of light . Very high values ​​for light refraction (n α  = 2.010; n β  = 2.110) and a very high value for birefringence (δ = 2.010) were found on the crystal grains of the Staněkit.

Under the microscope , the mineral is opaque in transmitted light, pale gray in incident (reflected) light and has very weak bireflectance and low reflection pleochroism . In immersion oil , the mineral is darker than in air, with a blue-gray hue. With crossed polars, the mineral shows moderate (in air) to significant (in immersion oil) anisotropy effects with pale brownish-gray rotational colors. The internal reflections vary from reddish-yellow to brownish-red and can be seen particularly clearly in the vicinity of microcracks and the grain boundaries.

No cleavage was recognized on the Staněkit , but good divisibility at right angles to the c-axis [001] was found. Due to its strong brittleness , however , it breaks like anhydrite , with the fracture surfaces being splintered. With a Mohs hardness of 4 to 5, the mineral is one of the medium-hard minerals and, like the reference minerals fluorite (hardness 4) and apatite (hardness 5), can be scratched more (fluorite) or less (apatite) with a pocket knife. The measured density of the mineral is 3.80 g / cm³, its calculated density is 4.09 g / cm³. The clear difference between the measured and calculated density is attributed to the foreign mineral inclusions contained in the Staněkit (mainly Kryzhanovskit). Staněkit is neither in the long term nor in the short wavelength UV light , a fluorescent .

Education and Locations

Staněkite could only be described as a very rare mineral formation from about 15 sites so far (status 2018). The type localities are the granite pegmatite Clementine II on the farm Okatjimukuju 55 (farm Friedrichsfelde) near Karibib, constituency Karibib in the Erongo region in Namibia as well as the pegmatite field near Collioure in the Albères massif , eastern Pyrenees , Occitania , France .

Staněkit is a typical secondary mineral due to its type locality , which has formed in the oxidation zone of a granite pegmatite with primary phosphate mineral paragenesis. It arose as a result of alteration processes at the expense of ferrisicklerite and heterosite or from triphylene . However, Staněkit has never been observed in adhesions with triphyline. If kryzhanovskite is present, it forms a seam between staněkite and heterositol.

Further investigations of countless thin sections have shown that both Staněkit polytypes did not emerge from the oxidation of Wolfeit, but were created in at least two steps through alteration processes at the expense of triphyline. First triphylene, Li (Fe, Mn, Mg) [PO 4 ], in ferrisicklerite, Li x (Mn, Mg) 2+ x (Fe) 3+ (1 – x) [PO 4 ] with x ≈ 0.5 converted, which was later replaced by Staněkit.

At the type locality, Staněkit can be found in three different parageneses :

  • Association I: Dendrites made from ferrisicklerite or heterosite with an Fe / (Fe + Mn) ratio of 0.78 are accompanied by eosphorite, arroyadite, kryzhanovskite and late-formed secondary phosphates.
  • Association II: Ferrisicklerite or heterosite with an Fe / (Fe + Mn) ratio of 0.61–0.68 in bulbous aggregates and occasional skeletal crystals. In addition to the accompanying minerals of Association I, Alluaudit is also available.
  • Association III: In addition to triphyline, above all Kryzhanovskit and the companions from Association II, as well as large amounts of late-formed secondary phosphates in the form of dense, dark green masses.

In the French Albères massif , staněkite is found in close association with ferrisicklerite and heterosite. All three minerals have an Fe / (Fe + Mn) ratio of 0.75, which suggests a more or less simultaneous crystallization.

In addition to the locations mentioned, Staněkit was also found in Namibia in the pegmatites "Cameroon" and "Sandamap" near Usakos and "Helikon" near Karibib. From the "Buranga pegmatite" near Gatumba , western province in Rwanda . From the "Cema pegmatite" near Las Aguadas , Departamento Libertador General San Martín , Province of San Luis in Argentina , and the "Lavra da Cigana" (Cigana claim) or "Lavra do Jocão" (Jocão pegmatite) near Conselheiro Pena in Minas Gerais , Brazil .

In Italy from a granite pegmatite within the "Bodengo-Pegmatite" in Val Soè / Val Bodengo, Valchiavenna , Province of Sondrio , Lombardy . In Spain from the "Julita" quarry in Cañada pegmatite, Garcirrey municipality, Salamanca province , Castile and León region , and pegmatites at Cabo de Creus in Catalonia .

In Poland from Lutomia in the municipality of Gmina Świdnica , district Świdnicki , and Michałkowa (Michelsdorf) in the Owl Mountains (Góry Sowie), Sudeten , both in Dolnośląskie .

Finally from pegmatites near Brissago on Lake Maggiore in the canton of Ticino , Switzerland . There are no known occurrences of Staněkit in Germany or Austria .

use

Naturally formed staněkite is rare and therefore only of interest to mineral collectors.

See also

literature

  • Paul Keller, François Fontan, Francisco Velasco Roldan, Joan Carles Melgarejo i Draper: Staněkite, Fe 3+ (Mn, Fe 2+ , Mg) (PO 4 ) O, a new phosphate mineral in pegmatites at Karibib (Namibia) and French Pyrénées (France) . In: European Journal of Mineralogy . tape 9 , no. 3 , 1997, p. 475–482 , doi : 10.1127 / ejm / 9/3/0475 ( rruff.info [PDF; 497 kB ; accessed on August 15, 2018]).
  • Paul Keller, Falk Lissner, Thomas Schleid: The crystal structure of staněkite, (Fe 3+ , Mn 2+ , Fe 2+ , Mg) [PO 4 ] O, from Okatjimukuju, Karibib (Namibia), and its relationship to the polymorphs of synthetic Fe 2 [PO 4 ] O . In: European Journal of Mineralogy . tape 18 , no. 3 , 2006, p. 113-118 , doi : 10.1127 / 0935-1221 / 2006 / 0018-0113 .

Web links

Individual evidence

  1. ^ A b Paul Keller, Oleg von Knorring: Pegmatites at the Okatjimukuju farm, Karibib, Namibia, part I: Phosphate mineral associations of the Clementine II pegmatite . In: European Journal of Mineralogy . tape 1 , no. 4 , 1989, pp. 567-594 , doi : 10.1127 / ejm / 1/4/0567 .
  2. ^ A b Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  443 .
  3. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am Paul Keller, François Fontan, Francisco Velasco Roldan, Joan Carles Melgarejo i Draper: Staněkite, Fe 3+ (Mn, Fe 2+ , Mg) (PO 4 ) O, a new phosphate mineral in pegmatites at Karibib (Namibia) and French Pyrénées (France) . In: European Journal of Mineralogy . tape 9 , no. 3 , 1997, p. 475–482 , doi : 10.1127 / ejm / 9/3/0475 ( rruff.info [PDF; 497 kB ; accessed on August 15, 2018]).
  4. ↑ a b c d e f Mindat - Staněkite (English)
  5. ^ IMA / CNMNC List of Mineral Names; March 2018 (PDF 1.65 MB)
  6. ↑ Typmineral catalog Germany - storage of the type material for Staněkit
  7. ^ A b Paul Keller, François Fontan, Francisco Velasco Roldan, Philippe de Parseval: Joosteite, Mn 2+ (Mn 3+ , Fe 3+ ) (PO 4 ) O: a new phosphate mineral from the Helikon II Mine, Karibib Namibia . In: New Yearbook for Mineralogy, Treatises . tape 183 , no. 2 , 2007, p. 197-201 , doi : 10.1127 / 0077-7757 / 2007/0069 .
  8. ↑ Paul Keller, Falk Lissner, Thomas Schleid: Crystal structure and polytypism of staněkite, (Fe 3+ , Mn 2+ , Fe 2+ , □) [PO 4 ] O . In: Journal of Crystallography, Supplement Issue . tape 22 , 2005, pp. 158 .
  9. ↑ a b c d e Paul Keller, Falk Lissner, Thomas Schleid: The crystal structure of staněkite, (Fe 3+ , Mn 2+ , Fe 2+ , Mg) [PO 4 ] O, from Okatjimukuju, Karibib (Namibia), and its relationship to the polymorphs of synthetic Fe 2 [PO 4 ] O . In: European Journal of Mineralogy . tape 18 , no. 3 , 2006, p. 113-118 , doi : 10.1127 / 0935-1221 / 2006 / 0018-0113 .
  10. Jump up ↑ Paul Keller, Falk Lissner, Thomas Schleid: The crystal structure of joosteite, (Mn 2+ , Mn 3+ , Fe 3+ ) 2 [PO 4 ] O, from the Helikon II mine, Karibib (Namibia), and its relationship to staněkite, (Fe 3+ , Mn 2+ , Fe 2+ , Mg) 2 [PO 4 ] O . In: New Yearbook for Mineralogy, Treatises . tape 184 , no. 2 , 2007, p. 225-230 , doi : 10.1127 / 0077-7757 / 2007/0095 .
  11. ↑ Mindat - Number of localities for Staněkit
  12. ↑ a b c d e List of locations where Staněkite was found in the Mineralienatlas and Mindat
  13. ↑ Encarnación Roda-Robles, Miguel A. Galliski, M. Belén Roquet, Frédéric Hatert, Philippe de Paeseval: Phosphate nodules containing two distinct assemblages in the Cema granitic pegmatite, San Luis province, Argentina: Paragenesis, composition and significance . In: Canadian Mineralogist . tape 50 , no. 4 , 2012, p. 913-931 , doi : 10.3749 / canmin.50.4.913 .
  14. ↑ Maxime Baijot, Frédéric Hatert, Fabrice Dal Bo, Simon Philippo: Mineralogy and petrography of phosphate mineral association from the Jocão pegmatite, Minas Gerais, Brazil . In: Canadian Mineralogist . tape 52 , no. 2 , 2014, p. 373-397 , doi : 10.3749 / canmin.52.2.373 .
  15. ↑ Alessandro Guastoni, Fabrizio Nestola, G. Mazzoleni, Pietro Vignola: Mn-rich graftonite, ferrisicklerite, staněkite and Mn-rich vivianite in a granitic pegmatite at Soè Valley, central Alps, Italy . In: Mineralogical Magazine . tape 71 , no. 5 , 2007, p. 579-585 , doi : 10.1180 / min mag.2007.071.5.579 .
  16. ↑ Encarnación Roda, Alfonso Pesquera, François Fontan, Paul Keller: Phosphate minerals associations in the Cañada pegmatite (Salamanca, Spain): paragenetic relationships, chemical compositions, and implications for pegmatite evolution . In: The American Mineralogist . tape 89 , no. 1 , 2004, p. 110-125 , doi : 10.2138 / am-2004-0114 .
  17. ^ Adam Pieczka, Bożena Gołębiowska, Andrzej Skowroński: Ferrisicklerite and other phosphate minerals from the Lutomia pegmatite (SW Poland, Lower Silesia, Góry Sowie Mts) . In: Jan Cempírek (Ed.): Book of Abstracts International Symposium on Light Elements in Rock-Forming Minerals . Nové Město na Moravě, Czech Republic, June 20–25, 2003. Masaryk University & Moravian Museum, Brno 2003, p. 63-64 (English).
  18. ^ Adam Pieczka, Krzysztof Witold Łobos, Michał Sachanbiński: The first occurrence of elbaite in Poland . In: Mineralogia Polonica . tape 35 , no. 5 , 2004, p. 579-585 ( edu.pl [PDF; 387 kB ; accessed on August 15, 2018]).
  19. ↑ Adam Pieczka, Adam Włodek, Bożena Gołębiowska, Eligiusz Szełęg, Adam Szuszkiewicz, Sławomir Ilnicki, Krzysztof Nejbert, Krzysztof Turniak: Phosphate-bearing pegmatites in the Góry Sowie Block and adjacent areas, Sudetes, SW Poland . In: Book of Abstracts 7th International Symposium on Granitic Pegmatites . PEG 2015 Książ, Poland. 2015, p. 77–78 (English, researchgate.net [PDF; 357 kB ; accessed on August 11, 2018]).
  20. ↑ Pietro Vignola, Valeria Diella, Paolo Oppizzi, Massimo Tiepolo, Stefan Weiss: Phosphate assemblages from the Brissago granitic pegmatite, Western Southern Alps, Switzerland . In: Canadian Mineralogist . tape 46 , no. 3 , 2008, p. 635–650 , doi : 10.3749 / canmin.46.3.635 ( silverchair-cdn.com [PDF; 1.4 MB ; accessed on August 15, 2018]).