Oxycalcioroméit

Oxycalcioroméit
Tiny oxycalcioroméite crystals in the calcite from the "Miniera di Buca della Vena" near Pontestazzemese in the municipality of Stazzema , Apuan Alps , Lucca Province , Tuscany , Italy
General and classification
other names	IMA 2012-022
chemical formula	Ca 2 Sb 2 O 6 O Ca 2 Sb 2 O 7
Mineral class (and possibly department)	Oxides and hydroxides
System no. according to Strunz	4.DH.15
Crystallographic Data
Crystal system	cubic
Crystal class ; symbol	cubic hexakisoctahedral; 4 / m  3  2 / m
Space group	Fd 3 m (No. 227)
Lattice parameters	a  = 10.3042  Å
Formula units	Z  = 8
Frequent crystal faces	{111}
Physical Properties
Mohs hardness	not definable
Density (g / cm 3 )	5.393 (calculated)
Cleavage	not specified
Break ; Tenacity	uneven; brittle
colour	reddish brown, reddish yellow
Line color	pale yellow
transparency	transparent
shine	Glass to resin gloss
Crystal optics
Refractive index	n  = 1.950
Optical character	isotropic

Oxycalcioroméit is a very rare mineral from the mineral class of oxides and hydroxides . It crystallizes in the cubic crystal system with the composition of Ca ₂ Sb ₂ O ₆ O, that is a calcium - antimonate whose Y position mainly by oxygen is occupied ions.

Oxycalcioroméit occurs at its type locality in the form of idiomorphic , octahedral crystals with a maximum size of 0.1 mm, which are closely associated with calcite , cinnabarite , derbylite , dolomite , hematite , mica , pyrite , sphalerite and tourmaline .

The type locality of the Oxycalcioroméits is the "Miniera di Buca della Vena" ( coordinates of the Miniera di Buca della Vena ) near Pontestazzemese in the municipality of Stazzema , Apuan Alps , Province of Lucca , Tuscany , Italy . The "Miniera di Buca della Vena" is already the type locality for Allanit- (La) , Apuanit , Dessauit- (Y) , Mapiquiroit , Marrucciit , Pellouxit , Pillait , Rouxelit , Scainiit , Stibivanit and Versiliait .

Etymology and history

Possibly identical to oxycalcioroméit: atopite

Orange-brown “Roméit” of the Atopit variety from Långban, Filipstad, Värmland, Sweden

Atopite by Miguel Prournier, Ouro Preto, Brazil

During the investigation of a mineral association from the "Miniera di Buca della Vena" near Stazzema, a representative of the pyrochlore upper group was identified who, on the basis of qualitative chemical analyzes by Paolo Orlandi and Andrea Dini, was first addressed as stibiobetafit . Stibiobetafit was originally defined by Petr Černý and colleagues (1979) as the Sb ³⁺ analogue of Betafit , but was redefined in the new nomenclature of the pyrochlore upper group to "Oxycalciopyrochlor". However, quantitative chemical analyzes on this mineral showed that the dominant element on the B position is not titanium , but antimony, which means that it is not a representative of the Betafit group , but a representative of the Roméit group . Chemical, spectroscopic and structural data showed the absence of H ₂ O and only a very low fluorine content, so that it is the Ca-Sb-O-dominant member of the pyrochlore upper group that has not yet been described as a mineral, according to the new nomenclature this group is called "Oxycalcioroméit". Chemical analyzes that correspond to an oxycalcioroméit had already been presented by Andrew G. Christy and Kjell Gatedal of a mineral from Långban , Filipstad municipality , Värmland County and the historical Värmland province in central Sweden , but the corresponding crystallographic data were missing.

After determining the physical, chemical and structural properties of the mineral from the "Miniera di Buca della Vena", it was submitted to the International Mineralogical Association (IMA), which recognized it in 2012 under the provisional designation IMA 2012-022 . The first scientific description of this mineral was made in 2013 by an Italian research team with Cristian Biagioni , Paolo Orlandi, Fabrizio Nestola and Sara Bianchin in the English science magazine Mineralogical Magazine . The authors named the 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 Sb and a Y position dominated by oxygen as oxycalcioroméite ( English Oxycalcioroméite ).

The type material for Oxycalcioroméit is kept under catalog number 19640 (holotype) in the collection of the “Museo di Storia Naturale” of the Università di Pisa in Pisa , Italy .

Roméit was a mineral named in 1841 by Augustin Alexis Damour in honor of Jean-Baptiste Romé de L'Isle , French mineralogist and one of the founders of crystallography, which was discredited when the nomenclature of the pyrochlore upper group was redefined in 2010 because it hide behind its composition the new minerals fluoronatroroméite, fluorcalcioroméite and oxycalcioroméite. He is also the namesake for the Roméit sub-group within the pyrochlore upper group. When the Atopit designated Roméit -Varietät then possibly also to Oxycalcioroméit.

classification

The current classification of the International Mineralogical Association (IMA) counts the oxycalcioroméit 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 ⁵⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Sb ⁵⁺ , W ⁶⁺ , Al ^3+, or Mg ²⁺ ; 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 Oxycalcioroméit still Fluorcalciomikrolith , Fluornatromikrolith , Hydrokenomikrolith , Hydroxycalciomikrolith , Hydroxykenomikrolith , Kenoplumbomikrolith , Oxynatromikrolith , Oxystannomikrolith , Oxystibiomikrolith , Cesiokenopyrochlor , Fluorcalciopyrochlor , Fluornatropyrochlor , Hydrokenopyrochlor , Hydropyrochlor , Hydroxycalciopyrochlor , Hydroxykenopyrochlor , Hydroxymanganopyrochlor , Hydroxynatropyrochlor , Oxycalciopyrochlor , Fluorcalcioroméit , Hydroxycalcioroméit , Hydroxyferroroméit , Oxyplumboroméite , Hydrokenoelsmoreit , Hydroxykenoelsmoreit , Fluornatrocoulsellit and Hydrokenoralstonit . Oxycalcioroméit forms together with fluorcalcioroméite, hydroxycalcioroméit, hydroxyferroroméite and oxyplumboroméit within the pyrochlore upper group the Roméit group .

The oxycalcioroméit is not yet listed in the outdated 8th edition of the Strunz mineral classification .

The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the IMA, classifies the oxycalcioroméit in the category of "Oxides with the molar ratio of metal: oxygen = 1: 2 and comparable". This is further subdivided according to the relative size of the cations involved and the crystal structure, so that the mineral is classified according to its composition and structure in the subsection “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. Oxycalcioroméit is with Fluorcalcioroméit , Fluornatroroméit , Hydroxycalcioroméit (formerly lewisite ) Oxyplumboroméite , Bismutostibiconit (Q), Monimolit (Q), Partzit (Q), Stetefeldtit (Q), Stibiconit to find (Q) in the Roméitgruppe.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world, also does not yet know the Oxycalcioroméit.

Chemism

Microprobe analyzes on oxycalcioroméite grains from the type locality yielded mean values ​​of 0.83% Na ₂ O; 13.68% CaO; 0.13% MnO; 0.68% PbO; 5.52% FeO; 0.28% Al ₂ O ₃ ; 0.68% V ₂ O ₃ ; 0.28% SnO ₂ ; 3.53% TiO ₂ ; 75.86% Sb ₂ O ₅ total; or 63.73% Sb ₂ O ₅ and 10.93% Sb ₂ O ₃ and 1.20% F; (O ≡ F) -0.51%; Sum = 100.96%. Based on two cations on the B position per formula unit, the empirical formula (Ca _1.073 Fe ²⁺ _0.338 Sb ³⁺ _0.330 Na _0.118 Pb ²⁺ _0.013 Mn ²⁺ _0.008 )) _{= 1.880} (Sb ⁵⁺ _1.734 Ti _0.194 V ³⁺ _0.040 Al _0.024 Sn ⁴⁺ _0.008 ) _{Σ = 2.000} (O _6.682 F _0.278 ) _{Σ = 6.960} , which has been simplified to Ca ₂ Sb ⁵⁺ ₂ O ₇ , which contains 25.74% CaO and 74.26% Sb ₂ O ₅ (total 100.00%) required.

Oxycalcioroméit is the only mineral with the element combination Ca - Sb - O. Chemically similar are u. a. Ingersonite , Ca ₃ Mn ²⁺ Sb ⁵⁺ ₄ O ₁₄ ; Peretaite , Ca (SbO) ₄ (SO ₄ ) ₂ (OH) ₂ • 2H ₂ O; Sarabauite , CaSb ³⁺ ₁₀ S ₆ O ₁₀ ; and the phases in question atopite , (Ca, Na) ₂ Sb ₂ (O, F, OH) ₇ , and mauzeliite , (Pb, Ca, Na) ₂ (Sb, Ti) ₂ (O, OH, F) ₇ .

Within the pyrochlore upper group there are theoretically a multitude of substitution possibilities due to the four different positions to be occupied. Oxycalcioroméite is the O-dominant analogue of the F-dominated fluoroccalcioroméite and the OH-dominated hydroxycalcioroméite as well as the Ca-dominant analogue of the Pb-dominated oxyplumboroméite. Across all subgroups, oxycalcioroméit is the Sb ⁵⁺ -dominant analogue of the Nb-dominated oxycalciopyrochloride (formerly stibiobetafit ).

Crystal structure

Crystal structure of oxycalcioroméite as a cation-centered polyhedral representation

Oxycalcioroméit crystallizes in the cubic crystal system in the space group Fd 3 m (space group no. 227) with the lattice parameter a = 10.3042  Å and eight formula units per unit cell .

The crystal structure of the Oxyplumboroméits (compare with the adjacent structural drawing) can be used as three-dimensionally polymerized, typical for representatives of the pyrochlore supergroup framework of corner-sharing B O ₆ - octahedra are described, wherein the tunnel by [110] exist in the interstices of this scaffolding which the Record A cations and the anions of the Y position. The eight-coordinate A position (16 d ) is mainly occupied by Ca. Since antimony occurs both as Sb ³⁺ and Sb ⁵⁺ in the oxycalcioroméite and only the Sb ⁵⁺ is located in the B- position , Sb ³⁺ must be incorporated in the A -position. Sb ³⁺ , however, sits on the split, less symmetrical A ′ position (96 g ), which is five times coordinated. The octahedrally coordinated B position ( 16c ) is not only occupied by Sb ^{5+ but also} to a small extent by Ti, Al, V ³⁺ and Sn ⁴⁺ . The X - (48 f ) and Y positions (8 b ) are four-coordinate anion positions and are occupied by O (48 f ) and O and subordinate F (8 b ). The oxygen environment around the B cations is roughly octahedral, while the A cations are located in distorted cubes.

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

properties

morphology

Oxycalcioroméit forms idiomorphic crystals 0.1 mm in size at its type locality, in which only the octahedron {111} has been identified.

physical and chemical properties

The crystals of the oxycalcioroméite are reddish brown to reddish yellow, while their stroke color is indicated as pale yellow. The surfaces of the transparent Oxycalcioroméit show a glass-like to resinous gloss , which corresponds very well with the high value for the refraction of light (n = 1.950). Oxycalcioroméit has no birefringence because it belongs to the cubic crystal system and is optically completely isotropic.

Oxycalcioroméit has no cleavage and no divisibility breaks but because of its brittleness like Amblygonit , wherein the fractured surfaces are formed uneven. Due to the small size of the crystals, neither the Mohs hardness nor the Vickers hardness could be determined. The calculated density for oxycalcioroméite is 5.393 g / cm³. Oxycalcioroméit is neither in the long wavelength even in the short wavelength UV light , a fluorescent .

Education and Locations

The type locality of the Oxycalcioroméits is the small barite - pyrite - deposit "Miniera di Buca della Vena" near Pontestazzemese in the municipality of Stazzema , Apuan Alps , province of Lucca , Tuscany , Italy , which is in contact between a metavolcanic-metasedimentary sequence of Palaeozoic-Triassic ages as well Upper Triassic dolomite stones and Lower Jurassic marbles . The lenticular ore body, 200 m long and a maximum of 20 m thick, is zoned and consists of barite and pyrite in its lower area and of barite and iron oxides ( magnetite and hematite ) in its upper area , with lenses made of marbles and dolomite stones in the ores. During the Alpine tectono-metamorphic event, these carbonate lenses were broken and deformed, forming calcite-barite vein systems in which oxycalcioroméite was developed alongside a number of rare mineral species. Oxycalcioroméit was found only on steps from the southern part of the pit. Its crystallization is closely related to the circulation of hydrothermal fluids during the alpine metamorphosis of the deposit, whereby the pressure - temperature conditions corresponded to the green slate facies .

Paragenesis minerals of the Fluorcalcioroméits in the "Miniera di Buca della Vena" are calcite , cinnabarite , derbylite , dolomite , hematite , mica , pyrite , sphalerite and tourmaline .

As a very rare mineral formation, the Oxycalcioroméit could so far (as of 2018) only be described from five sites worldwide.

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

• the "Blocherleitengraben" in the Mieslingtal near Spitz , Wachau , Lower Austria , Austria
• the discarded Cu-Sb mine of the "Mina da Herdade da Ventosa" near Nossa Senhora das Neves , Beja , Distrito de Beja , Alentejo region , Portugal
• the metamorphic Fe-Mn deposit Långban , Filipstad municipality , Värmland County or the historic Värmland province in central Sweden
• the "Fianel" mine not far from the Ausserferrera fraction of the municipality of Ferrera GR in the south of the former Hinterrhein district of the canton of Graubünden , Switzerland

Locations for Oxycalcioroméit in Germany are therefore unknown.

use

Oxycalcioroméit is because of its rarity without any practical meaning and only interesting for mineral collectors.

See also

• Systematics of the minerals
• List of minerals

literature

• Cristian Biagioni, Paolo Orlandi, Fabrizio Nestola, Sara Bianchin: Oxycalcioroméite, Ca ₂ Sb ₂ O ₆ O, from Buca della Vena mine, Apuan Alps, Tuscany, Italy: a new member of the pyrochlore supergroup . In: Mineralogical Magazine . tape 77 , 2013, p. 3027–3037 , doi : 10.1180 / minmag.2013.077.7.12 (English).

Web links

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

• Mineral Atlas: Oxycalcioroméit (Wiki)
• Oxycalcioroméite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 29, 2020 . 
• American-Mineralogist-Crystal-Structure-Database - Oxycalcioroméite. In: rruff.geo.arizona.edu. Retrieved April 29, 2020 . 

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} Cristian Biagioni, Paolo Orlandi, Fabrizio Nestola, Sara Bianchin: Oxycalcioroméite, Ca ₂ Sb ₂ O ₆ O, from Buca della Vena mine, Apuan Alps, Tuscany, Italy: a new member of the pyrochlore supergroup . In: Mineralogical Magazine . tape 77 , 2013, p. 3027–3037 , doi : 10.1180 / minmag.2013.077.7.12 (English).
2. ↑ ^{a b c} Paolo Orlandi, Andrea Dini: The minerals of the Buca della Vena mine, Apuan mountains, Tuscany (Italy) . In: Lapis . tape 29 , no. 1 , 2004, p. 11–24 (as stibiobetafite).
3. ^ ^{A b} Petr Černý, Frank C. Hawthorne, Joseph Hector Gilles Laflamme, James Hinthorne: Stibiobetafite, a new member of the Pyrochlore Group from Vezná, Czechoslovakia . In: The Canadian Mineralogist . tape 17 , 1979, pp. 583-588 (English, rruff.info [PDF; 751 kB ; accessed on October 3, 2018]).
4. ↑ ^{a b c d e} 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 August 30, 2018]).
5. ↑ Andrew G. Christy, Kjell Gatedal: Extremely Pb-rich rock-forming silicates including a beryllian scapolite and associated minerals in a skarn from Långban, Värmland, Sweden . In: Mineralogical Magazine . tape 69 , no. 6 , 2005, p. 995-1018 , doi : 10.1180 / 0026461056960304 (English).
6. ^ 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, main.jp [PDF; 85 kB ; accessed on August 30, 2018]).
7. ↑ atopites. In: mindat.org. Hudson Institute of Mineralogy, accessed April 29, 2020 .  
8. ↑ ^{a b c} Oxycalcioroméite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 29, 2020 .  
9. ^ Daniel Atencio, Marco E. Ciriotti Marcello B. Andrade: Fluorcalcioroméite, (Ca, Na) ₂ Sb ⁵⁺ ₂ (O, OH) ₆ F, a new roméite-group mineral from Starlera mine, Ferrera, Grischun, Switzerland: Description and crystal structure . In: Mineralogical Magazine . tape 77 , no. 4 , 2012, p. 467–473 , doi : 10.1180 / minmag.2013.077.4.06 (English, researchgate.net [PDF; 939 kB ; accessed on October 26, 2018]).
10. ^ 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, Lewisite and zirkelite ... ( Memento from August 12, 2017 in the Internet Archive ) [PDF; 331 kB ; accessed on April 29, 2020]).
11. ↑ Ulf Hålenius, Ferdinando Bosi: Oxyplumboroméite, Pb ₂ Sb ₂ O ₇ , a new mineral species of the pyrochlore supergroup from Harstigen mine, Värmland, Sweden . In: Mineralogical Magazine . tape 77 , no. 7 , 2013, p. 2931–2939 , doi : 10.1180 / minmag.2013.077.7.04 (English).
12. ↑ Localities for Oxycalcioroméite. In: mindat.org. Hudson Institute of Mineralogy, accessed April 29, 2020 .  
13. ↑ ^{a b} List of locations for Oxycalcioroméit in the Mineralienatlas and Mindat , accessed on April 29, 2020.