Hydroxycalciopyrochlor

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Hydroxycalciopyrochlor
General and classification
other names

IMA 2011-026

chemical formula (Ca, Na, U, □) 2 (Nb, Ti) 2 O 6 (OH)
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.DH.15 ( 8th edition : IV / C.17)
02/08/01. ??
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Fd 3 m (No. 227)Template: room group / 227
Lattice parameters a  = 10.381  Å
Formula units Z  = 8
Frequent crystal faces {111}, {110}, {210}
Physical Properties
Mohs hardness 5.5; Vickers hardness VHS = 572 kg / mm²
Density (g / cm 3 ) 5.10 (measured); 4.99 to 5.31 (calculated)
Cleavage no
Break ; Tenacity clamshell; brittle
colour brownish black, greenish black, black; Brown in transmitted light, gray in reflected light
Line color brown
transparency translucent
shine Diamond luster, rarely greasy luster
Crystal optics
Refractive index n  > 1.9
Optical character isotropic
Other properties
Chemical behavior resistant to HCl or HNO 3 , but soluble in H 3 PO 4
Special features metamict

Hydroxycalciopyrochlor is a very rare mineral from the mineral class of oxides and hydroxides . It crystallizes in the cubic crystal system with the composition (Ca, Na, U, □) 2 (Nb, Ti) 2 O 6 (OH), so it is a calcium - sodium - niobate with additional hydroxide ions.

Hydroxycalciopyrochlor occurs at its type locality in the form of idiomorphic crystals with a maximum size of 1 mm, which form octahedra , rhombic dodecahedron , tetrakis hexahedron or combinations of these flat shapes. In another deposit, the “Václav” graphite mine near Bližná not far from České Budějovice , Czech Republic , the mineral forms rounded grains up to 3 cm in diameter and idiomorphic crystals up to 2 mm in size.

The type locality of the hydroxycalciopyrochloride is the “Maoniuping” deposit ( coordinates of the REE “Maoniuping” deposit ) in Mianning County , Liangshan Autonomous District , Sichuan Province , People's Republic of China . This is the world's second largest REE deposit .

Etymology and history

As early as 1991, Yang & Yan described a mineral from the “Maoniuping” deposit in accordance with the then valid classification as betafit , while the same mineral was designated as calciobetafite in 2003 by Zhang Ru-Bo and colleagues . After the introduction of the guidelines for the new pyrochlore upper group, this mineral proved to be a new representative of this upper group and, after determining the corresponding properties, was submitted to the International Mineralogical Association (IMA), which recognized it in 2011 under the provisional designation "IMA 2011-026" . The first scientific description of this mineral was made in 2014 by a Chinese research team with Yang Guangming, Li Guowu, Xiong Ming, Pan Baoming and Yan Chenjie in the Chinese science magazine Acta Geologica Sinica .

The authors named the new mineral in accordance with the nomenclature of the pyrochlore upper group due to its chemical composition with an A position dominated by calcium , a B position dominated by niobium and a Y position dominated by hydroxyl groups as hydroxycalciopyrochlor ( English: hydroxycalciopyrochlore ).

The type material for Hydroxycalciopyrochlore is kept in the collection of the Chinese Geological Museum in Beijing , China, under catalog number M11800 (holotype) .

In the past minerals from different deposits, which were the chemical composition of a Hydroxycalciopyrochlors had, in a series of publications as pyrochlore , Hydropyrochlor or Betafit described. Pyrochlore itself was found by Nils Otto Tank (1800–1864) near Stavern in the Norwegian province of Vestfold and described in 1826 by Friedrich Wöhler . Wöhler named the mineral based on a suggestion by Jöns Jakob Berzelius after the Greek words πῦς [ pyr ] and χλωρός [ chlorós ] for "fire" and "green" because of its property, after melting with phosphorus salt (sodium ammonium hydrogen phosphate) before Solder tube to solidify to a grass-green glass. Over the decades, the term pyrochlore has often been used unspecifically and often without the background of chemical analysis. The mineral pyrochlore was discredited in 2010.

classification

The current classification of the International Mineralogical Association (IMA) counts the hydroxycalciopyrochlore to the pyrochlore upper group with the general formula A 2– m B 2 X 6– w Y 1– n , in which A , B , X and Y different positions in the structure the minerals of the pyrochlore upper group with A  = Na, Ca, Sr, Pb 2+ , Sn 2+ , Sb 3+ , Y, U, □, or H 2 O; B = Ta, Nb, Ti, Sb 5+ or W; X = O, OH or F and Y = OH - , F, O, □, H 2 O or very large (>> 1.0 Å) monovalent cations such as K, Cs or Rb. To pyrochlore supergroup include not only Hydroxycalciopyrochlor still Fluorcalciomikrolith , Fluornatromikrolith , Hydrokenomikrolith , Hydroxycalciomikrolith , Hydroxykenomikrolith , Kenoplumbomikrolith , Oxynatromikrolith , Oxystannomikrolith , Oxystibiomikrolith , Cesiokenopyrochlor , Fluorcalciopyrochlor , Fluornatropyrochlor , Hydrokenopyrochlor , Hydropyrochlor , Hydroxykenopyrochlor , Hydroxymanganopyrochlor , Hydroxynatropyrochlor , Oxycalciopyrochlor , Fluorcalcioroméit , Hydroxycalcioroméit , Hydroxyferroroméit , Oxycalcioroméit , Oxyplumboroméite , Hydrokenoelsmoreit , Hydroxykenoelsmoreit , Fluornatrocoulsellit and Hydrokenoralstonit . Hydroxycalciopyrochlor, together with cesiokenopyrochlor, fluorcalciopyrochlor, fluoronatropyrochlor, hydrokenopyrochlor, hydropyrochlore, hydroxykenopyrochlor, hydroxymanganopyrochlor, hydroxynatropyrochlor and oxycalciopyrochlor within the pyrochlore upper group, forms the pyrochlore group .

The 8th edition of the mineral classification according to Strunz , which is now outdated, but still in use in some cases, does not yet list hydroxycalciopyrochloride. It would belong to the mineral class of "oxides and hydroxides" and there to the general division of "oxides with a metal: oxygen ratio = 2: 3 (M 2 O 3 and related compounds)", where together with bariopyrochlore (discredited 2010, possibly " Zero-valent-dominant pyrochlore "), bismuthopyrochlore (discredited 2010, possibly" Oxynatropyrochlore "), Calciobetafit (discredited 2010), Ceriopyrochlor- (Ce) (discredited 2010, possibly" Fluorkenopyrochlore "), Kalipyrochlore (2010 redefined to hydropyrochlore), Plumbopyrochlor (discredited 2010, possibly "Oxyplumbopyrochlor" or "Kenoplumbopyrochlor"), Pyrochlore (discredited 2010, since then group and parent group name; this includes the possibly new species "Oxynatropyrochlor", "Hydroxycalciopyrochlor", "Fluorcalciopyrochlor" and "Fluorkenopyrochlor"), Uranpyrochlor (discredited 2010, possibly “Oxynatropyrochlor”), Strontiopyrochlor (discredited 2010, possibly “Fluorstrontiopyroc hlor "or" Fluorkenopyrochlor ") and Yttropyrochlor- (Y) (discredited 2010, possibly" Oxyyttropyrochlor- (Y) ") the" Pyrochlore Group, Pyrochlore Subgroup "with the system no. IV / C.17 would have 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), classifies the hydroxycalciopyrochlore in the category of "oxides with the molar ratio metal: oxygen = 1: 2 and comparable". However, this section is further subdivided according to the relative size of the cations involved and the crystal structure, so that the mineral according to its composition and structure is classified in the sub-section “With large (± medium-sized) cations; Layers of edge-linked octahedra ”can be found, where together with all representatives of the pyrochlore, microlith, Betafit, Roméit and Elsmoreit groups, the pyrochlore supergroup with the system no. 4.DH.15 forms. Hydroxycalciopyrochlor is together with Fluorcalciopyrochlor , Fluornatropyrochlor , Fluorkenopyrochlor , Fluorstrontiopyrochlor , Hydropyrochlor (formerly Kalipyrochlor ) Kenoplumbopyrochlor , Oxycalciopyrochlor (formerly Stibiobetafit ) Oxynatropyrochlor , Oxyplumbopyrochlor and Oxyyttropyrochlor- (Y) to be found in the Pyrochlorgruppe.

Also the systematics of minerals according to Dana , which is mainly used in the English-speaking area , does not yet know the hydroxycalciopyrochloride. It would be classified in the class of "oxides and hydroxides", but there in the department of "multiple oxides with Nb, Ta and Ti". Here he was, along with pyrochlore , Kalipyrochlor , Bariopyrochlor , Yttropyrochlor- (Y) , Ceriopyrochlor- (Ce) , Plumbopyrochlor , Uranpyrochlor , Strontiopyrochlor and Bismutopyrochlor (all since 2010 discredited. See under classification of minerals by Strunz 8th edition) the "pyrochlore subgroup; Nb> Ta; (Nb + Ta)> 2 (Ti) “with the system no. 08.02.01 to be found within the subsection of " Multiple oxides with Nb, Ta and Ti with the formula A 2 (B 2 O 6 ) (O, OH, F) ".

Chemism

Ten microprobe analyzes on four individual grains yielded mean values ​​of 4.25% Na 2 O; 9.89% CaO; 0.42% FeO; 0.08% MgO; 0.11% PbO; 0.26% ThO 2 ; 25.87% UO 2 ; 2.02% Ce 2 O 3 ; 0.13% Y 2 O 3 ; 15.23% TiO 2 ; 0.15% Al2O3; 36.36% Nb 2 O 5 ; 1.78% Ta 2 O 5 ; 0.36% F; 2.15% H 2 O and [(2F ≡ O) -0.16%, sum = 98.92%]. On the basis of two cations per formula unit in the B position, the empirical formula (Ca 0.73 Na 0.57 U 0.40 Ce 0.05 Fe 0.02 Y 0.01 □ 0.22 ) Σ = 2.00 (Nb 1.14 Ti 0.79 Ta 0.03 Al 0.01 Mg 0.01 ) Σ = 2.00 O 6.02 [(OH) 1.01 F 0.09 ] Σ = 1, 10 which has been simplified to (Ca, Na, U, □) 2 (Nb, Ti) 2 O 6 (OH).

Due to the high content of uranium and thorium , the hydroxycalciopyrochlore of the type locality is metamictic .

Of all the minerals, only hydroxycalciopyrochlore contains the element combination Ca - Nb - O - (OH). In addition, Charleshatchettite , CaNb 4 O 10 (OH) 2 · 8H 2 O, Hochelagaite , (Ca, Na, Sr) (Nb, Ti, Si, Al) 4 O 11 · 8H 2 O, and "UM1986-21- NbO: CaH "( Mont Saint-Hilaire " MSH UK-56 ", unnamed), but also Fersmit , (Ca, Ce, Na) (Nb, Ta, Ti) 2 (O, OH, F) 6 , and hydroxymanganopyrochlor , (Mn 2+ , Th, Na, Ca, REE) 2 (Nb, Ti) 2 O 6 (OH), chemically similar compositions. The cation positions chemically also similar, but siliceous , are Alluaivit , Andrianovit , Bobtraillit , Burovait-Ca , Calciomurmanit , Carbokentbrooksit , Eveslogit , Feklichevit , Ferrokentbrooksit , Georgbarsanovit , Golyshevit , Haineaultit , Janhaugit , Karupmøllerit-Ca , Kentbrooksit , Låvenit , Oneillit , Paratsepinit -Na , Raslakit , Siudait , Taseqit and Tienshanit .

Within the pyrochlore upper group there are theoretically a multitude of substitution possibilities due to the four different positions to be occupied. Hydroxycalciopyrochlor is the OH-dominant analogue to the F-dominated fluorocalciopyrochlore and the Ca-dominant analogue to the vacancy-dominated hydroxykenopyrochlore, to the Mn-dominant hydroxymanganopyrochore and to the Na-dominated hydroxynatropyrochlore. Across all subgroups, hydroxycalciopyrochloride is the Nb-dominant analogue of the Ta-dominated hydroxycalciomicrolite and the Sb 5+ -dominated hydroxycalcioroméite.

Crystal structure

Hydroxycalciopyrochlor crystallizes in the cubic crystal system in the space group Fd 3 m (space group no. 227) with the lattice parameter a = 10.381  Å and eight formula units per unit cell . Template: room group / 227

The crystal structure of the Hydroxycalciopyrochlors is by edge-sharing (Nb, Ti) O 6 - octahedron characterized, form the chains in the direction of [110]. The atoms on the A position (calcium, sodium, uranium and vacancies, □) are eight-fold coordinated and sit in the gaps within the network of B O 6 octahedra. The structure can be also as a combination of A O 8 - hexahedrons and B O 6 octahedra common edges describe the atoms on the A position in the center of cube-shaped polyhedra sit whose corners of oxygen -atoms and (OH) - Ions are formed.

Hydroxycalciopyrochlor is isotypic (isostructural) to all other representatives of the pyrochlore upper group which crystallize in the space group Fd 3 m (space group no. 227) . Template: room group / 227

properties

morphology

Hydroxycalciopyrochlor occurs at its type locality mostly in the form of idiomorphic crystals with a maximum size of 1 mm, which form octahedra , rhombic dodecahedron , tetrakis hexahedron like {210} or combinations of these flat shapes. Occasionally there are also distorted, thick tabular crystals with a triangular cross-section. In the “Václav” graphite mine near Bližná not far from České Budějovice , Czech Republic , the mineral forms rounded grains up to 3 cm in diameter and idiomorphic crystals up to 2 mm in size.

physical and chemical properties

The hydroxycalciopyrochloride crystals are brownish-black, greenish-black or black at the type locality, but their line color is always brown. The crystals are often covered with a thin, powdery yellow coating. The mineral is brown in the transmitted light in the thin section and gray in the reflected light. The surfaces of the translucent Hydroxycalciopyrochlors show a diamond-like, rarely also greasy luster , which agrees well with the very high value for the refraction of light (n = 1.9). Hydroxycalciopyrochlor is optically isotropic.

Hydroxycalciopyrochlor has neither cleavage nor divisibility. Due to its brittleness , however , it breaks in a similar way to quartz , with the fracture surfaces being shell-shaped. With a Mohs hardness of 5.5, the mineral is one of the medium-hard minerals and is thus between the reference minerals apatite (hardness 5) and orthoclase (hardness 6), which can still be found with a pocket knife (apatite) or with a steel file (orthoclase) let scratch. Its Vickers hardness VHS was determined to be 572 kg / mm². The measured density for hydroxycalciopyrochlore is 5.10 g / cm³, the calculated density is 4.99 to 5.31 g / cm³.

There is no information on fluorescence in UV light or on cathodoluminescence under the electron beam for the mineral.

Hydroxycalciopyrochlor is insoluble in hydrochloric acid , HCl, and nitric acid , HNO 3 , but dissolves in phosphoric acid , H 3 PO 4 , and more easily in warm than cold.

Education and Locations

The type locality for hydroxycalciopyrochlore is the Maoniuping deposit in Mianning County , Liangshan Autonomous District , Sichuan Province , People's Republic of China . In this world's second largest deposit of rare earth metals, originally excavated as a molybdenum mine , 0.4 million tons of ore with a content of 2% REE 2 O 3 were detected. The deposit consists of bastnasite-barite-carbonate veins, which are associated with northern Markites and sit in a carbonatite - syenite complex. This complex is located in the Panzhihua-Xichang Rift, a north-south trending regional pull-apart rift structure that formed during the late Paleozoic .

Hydroxycalciopyrochlor was found in the REE ore of the alkali feldspar granite . The rock mass is located in the northern zone of the Panzhihua-Xichang Rift and belongs to the eastern edge of the Xichang-Lizhuang granite body. Hydroxycalciopyrochlor was also observed here in an aegirine - barite - calcite- RREE ore. In addition to the accompanying minerals mentioned, hydroxycalciopyrochlore is also accompanied by celestine , albite , aegirine-augite , fluorite , parisite (Ce) , thorite , thorianite , zirconium , galena , sphalerite , magnetite and pyrite .

As a very rare mineral formation, the Hydroxycalciopyrochlor could so far (as of 2018) only be described from around ten sites.

In addition to the type locality, the following sites are known:

Locations for Hydroxycalciopyrochlor in Austria and Switzerland are therefore unknown.

use

Hydroxycalciopyrochlor would be a rich niobium ore due to its Nb 2 O 5 content of 30.40-43.86 wt%. However, due to its rarity, the mineral is of no practical importance.

See also

literature

  • Yang Guangming, Li Guowu, Xiong Ming, Pan Baoming, Yan Chenjie: Hydroxycalciopyrochlore, a new mineral species from Sichuan, China . In: Acta Geologica Sinica (english edition) . tape 88 , no. 3 , 2014, p. 748-753 , doi : 10.1111 / 1755-6724.12235 (English).

Web links

Commons : Pyrochlore  - collection of images, videos and audio files

Individual evidence

  1. ↑ 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 Yang Guangming, Li Guowu, Xiong Ming, Pan Baoming, Yan Chenjie: Hydroxycalciopyrochlore, a new mineral species from Sichuan, China . In: Acta Geologica Sinica (english edition) . tape 88 , no. 3 , 2014, p. 748-753 , doi : 10.1111 / 1755-6724.12235 (English).
  2. ^ Donald David Hogarth: Classification and nomenclature of the pyrochlore group . In: The American Mineralogist . tape 62 , 1977, pp. 403–410 (English, rruff.info [PDF; 869 kB ; accessed on September 12, 2019]).
  3. ↑ Yang G., Yan C .: Betafite in aegirine alkali feldspar granite massif, Mianning county, Sichuan province, China . In: Journal of Mineralogy and Petrology . tape 11 , 1991, p. 9–13 (English, Chinese, abstract).
  4. ^ Zhang Ru-bo, Du Chong-liang, Long Zao-yun: The discovery of calciobetafite in China . In: Journal of Mineralogy and Petrology . tape 23 , 2003, p. 5–8 (in Chinese with an English abstract).
  5. ↑ Dmitriy I. Belakovskiy, Fernando Cámara, Olivier C. Gagne, Yulia Uvarova: New mineral names . In: American Mineralogist . tape 100 , no. 7 , 2015, p. 2352–2362 , doi : 10.2138 / am-2015-NMN1001010 (English, minsocam.org [PDF; 423 kB ; accessed on September 12, 2019] Dmitriy I. Belakovskiy: Hydroxycalciopyrochlore, pp. 2359-2360).
  6. ↑ a b Friedrich Wöhler: About the pyrochlore, a new mineral species . In: Poggendorff's annals of physics and chemistry . tape 7 , no. 4 , 1826, pp. 417-428 ( limited preview in Google Book search).
  7. ^ A b Daniel Atencio, Marcelo B. Andrade, Andrew G. Christy, Reto Gieré, Pavel M. Kartashov: The Pyrochlore supergroup of minerals: Nomenclature . In: The Canadian Mineralogist . tape 48 , 2010, p. 673–698 , doi : 10.3749 / canmin.48.3.673 (English, rruff.info [PDF; 1,4 MB ; accessed on September 12, 2019]).
  8. ^ Andrew G. Christy, Daniel Atencio: Clarification of the status of species in the pyrochlore supergroup . In: Mineralogical Magazine . tape 77 , no. 1 , 2013, p. 13–20 , doi : 10.1180 / minmag.2013.077.1.02 (English, cnmnc.main.jp [PDF; 80 kB ; accessed on September 12, 2019]).
  9. ↑ a b Li Guowu, Yang Guangming, Lu Fude, Xiong Ming, Ge Xiangkun, Pan Baoming, Jeffrey de Fourestier: Fluorcalciopyrochlor, a new mineral species from Bayan Obo, Inner Mongolia, PR China . In: The Canadian Mineralogist . tape 54 , no. 5 , 2016, p. 1285–1291 , doi : 10.3749 / canmin.1500042 (English).
  10. ↑ a b c d Hydroxycalciopyrochlore. In: mindat.org. Hudson Institute of Mineralogy, accessed September 12, 2019 .
  11. ↑ Ritsuro Miyawaki, Koichi Momma, Satoshi Matsubara, T. Sano, Masako Shigeoka, H. Horiuchi: Hydroxykenopyrochlore, IMA 2017-030a. CNMNC Newsletter No. 39, October 2017, page 1285 . In: Mineralogical Magazine . tape 81 , 2017, p. 1279-1286 (English).
  12. ↑ Nikita V. Chukanov, Günter Blass, Natalia V. Zubkova, Igor V. Pekov, Dmitry Yu. Pushcharovskii, Heribert Prinz: Hydroxymanganopyrochlore: A New Mineral from the Eifel Volcanic Region, Germany . In: Doklady Earth Sciences . tape 449 , no. 1 , 2013, p. 342-345 , doi : 10.1134 / S1028334X13030100 (English).
  13. ↑ Gregory Yu. Ivanyuk, Victor N. Yakovenchuk, Taras L. Panikorovskii, Nataliya Konoplyova, Yakov A. Pakhomovsky, Ayya V. Bazai, Vladimir N. Bocharov, Sergey V. Krivovichev: Hydroxynatropyrochlore, (Na, С a, Ce) 2 Nb 2 O 6 (OH), a new member of the pyrochlore group from the Kovdor phoscorite-carbonatite pipe (Kola Peninsula, Russia) . In: Mineralogical Magazine . 2018, doi : 10.1180 / minmag.2017.081.102 (English).
  14. ↑ Marcelo B. Andrade, Hexiong Yang, Daniel Atencio, Robert T. Downs, Nikita V. Chukanov, Marie-Hélène Lemée-Cailleau, Aba Israel Cohen Persiano, Andrés E. Goeta, Javier Ellena: Hydroxycalciomicrolite, Ca 1.5 Ta 2 O 6 (OH), a new member of the microlite group from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil . In: Mineralogical Magazine . tape 81 , no. 3 , 2017, p. 555–564 , doi : 10.1180 / minmag.2016.080.116 (English).
  15. ^ Franz Eugen Hussak, George Thurland Prior: Lewisite and zirkelite, two new Brazilian minerals . In: Mineralogical Magazine . tape 11 , 1895, p. 80–88 , doi : 10.1180 / minmag.1895.011.50.05 (English, rruff.info [PDF; 331 kB ; accessed on September 12, 2019]).
  16. ↑ a b Milan Drábek, Jiří Frýda, Michal Šarbach, Roman Skála: Hydroxycalciopyrochlore from a regionally metamorphic marble at Bližná, Southwestern Czech Republic . In: New Yearbook for Mineralogy, Treatises . tape 194 , no. 1 , 2017, p. 49–59 , doi : 10.1127 / njma / 2016/0014 (English).
  17. ↑ Localities for Hydroxycalciopyrochlor. In: mindat.org. Hudson Institute of Mineralogy, accessed September 12, 2019 .
  18. ↑ a b List of locations for Hydroxycalciopyrochlor in the Mineralienatlas and Mindat (accessed on September 29, 2018)