Hydroxycalcioroméit

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Hydroxycalcioroméit
General and classification
other names

Lewisite

chemical formula
  • (Ca, Sb 3+ ) 2 (Sb 5+ , Ti) 2 O 6 (OH)
  • (Ca, Sb 3+ , Fe 3+ , Al, Na, Mn, □) 2 (Sb 5+ , Ti) 2 O 6 (OH) (as Lewisite )
  • (Ca, Fe 2+ , Na) 2 (Sb, Ti) 2 O 7 (as Lewisite )
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.DH.15 ( 8th edition : none)
01/44/01/04 ( Lewisite )
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  = 10.264  Å
Formula units Z  = 8
Frequent crystal faces {111}
Twinning rarely after (111)
Physical Properties
Mohs hardness 5.5
Density (g / cm 3 ) 4.95 (measured), 5.31 (calculated)
Cleavage very perfect after {111}
Break ; Tenacity half-mussel; not brittle
colour honey yellow to colophony brown, amber yellow, golden yellow, yellow brown, orange brown
Line color light yellowish brown
transparency translucent to translucent
shine Glass to resin gloss, semi-glass gloss
Crystal optics
Optical character isotropic
Pleochroism none
Other properties
Chemical behavior Insoluble in acids, but decomposable by melting with sodium carbonate

Hydroxycalcioroméit is a rare mineral belonging to the mineral class of oxides and hydroxides . It crystallizes in the cubic crystal system with the composition (Ca, Sb 3+ ) 2 (Sb 5+ , Ti) 2 O 6 (OH), so it is a calcium - antimony - antimonate with additional hydroxide ions .

Hydroxycalcioroméit is found in the form of idiomorphic, homogeneous, octahedral crystals up to 1 mm in size and in the form of earthy masses. Its type locality is the cinnabarite mine "Fazenda Tres Cruzes" , which is built in alluvial sands near Tripuí (formerly Tripuhy) ( coordinates of the cinnabarite mine Tripuí ) in the Ouro Preto district near Ouro Preto , Minas Gerais in Brazil .

Etymology and history

In the heavy mineral sands of the cinnabarite mine near Tripuí, not far from Ouro Preto, Minas Gerais, Brazil, known since 1810 and first described by Wilhelm Ludwig von Eschwege in 1833 , Franz Eugen Hussak and George Thurland Prior found, along with other heavy minerals, a tiny octahedron-forming mineral, which is called titano -Antmonth of calcium and iron and thus proved to be a new mineral. Hussak & Prior published the first scientific description for the new mineral in 1895 in the English science magazine "Mineralogical Magazin" and named the mineral in honor of the professor of mineralogy at the University of Cambridge William James Lewis (1847-1926) for his services to the study of mineralogy as Lewisite ( English Lewisite ).

In the course of the replacement of common names by systematic names, the mineral was discredited in 2007 by Ernst AJ Burke and renamed to Ti-containing Roméit . During the revision of the nomenclature of the "pyrochlore group" to the new pyrochlore upper group (pyrochlore supergroup) it was determined that the representative of the pyrochlore upper group with an A position dominated by calcium in the crystal lattice, dominated by Sb dominated B position and by OH Y position with the new, nomenclature-compliant name Hydroxycalcioroméit ( English Hydroxycalcioroméite ) is to be designated. The type material of Lewisite defined by Hussak & Prior in 1895 is now considered to be the type material (holotype) for hydroxycalcioroméite. The term "Lewisite" has been discredited.

The type material for hydroxycalcioroméite (Lewisite) is stored under catalog number 80141 in the collection of the Natural History Museum , London , England , and under catalog number R5741 in the collection of the National Museum of Natural History , Washington, DC , USA , which is part of the Smithsonian Institution .

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.

classification

The current classification of the International Mineralogical Association (IMA) counts the hydroxycalcioroméit 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 have 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 Hydroxycalcioroméit still Fluorcalciomikrolith , Fluornatromikrolith , Hydrokenomikrolith , Hydroxycalciomikrolith , Hydroxykenomikrolith , Kenoplumbomikrolith , Oxynatromikrolith , Oxystannomikrolith , Oxystibiomikrolith , Cesiokenopyrochlor , Fluorcalciopyrochlor , Fluornatropyrochlor , Hydrokenopyrochlor , Hydropyrochlor , Hydroxycalciopyrochlor , Hydroxykenopyrochlor , Hydroxymanganopyrochlor , Hydroxynatropyrochlor , Oxycalciopyrochlor , Fluorcalcioroméit , Hydroxyferroroméit , Oxycalcioroméit , Oxyplumboroméite , Hydrokenoelsmoreit , Hydroxykenoelsmoreit , Fluornatrocoulsellit and Hydrokenoralstonit . Hydroxycalcioroméite (formerly Lewisite) forms the Roméite group within the pyrochlore upper group together with fluorocalcioroméite, hydroxyferroroméite, oxycalcioroméite and oxyplumboroméite .

The 8th edition of the mineral systematics according to Strunz , which is now outdated, but still in use in some cases , lists neither the hydroxycalcioroméite nor the lewisite .

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 hydroxycalcioroméite (formerly Lewisite ) 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. Hydroxycalcioroméit (formerly Lewisite ) is, together with Fluorcalcioroméit , Fluornatroroméit , Oxycalcioroméit , Oxyplumboroméite , Bismutostibiconit (Q), Monimolit (Q), Partzit (Q), Stetefeldtit (Q) and Stibiconit (Q) found in the Roméitgruppe.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , does not yet know the hydroxycalcioroméite, but assigns the lewisite to the class of "phosphates, arsenates and vanadates" and there in the department of " antimonates ". Here it is together with stibiconite, bindheimite, roméite, monimolite, stetefeldite, bismuthostibiconite and partzite in the stibiconite group with system no. 44.01.01 to be found in the subsection " Antimonates A (X 2 O 6 ) ".

Chemism

For Lewisite the ideal formula 5CaO · 3Sb was calculated from the results of two wet chemical analysis initially 2 O 5 · 2TiO 2 determines what an empirical formula of Ca 5 Sb 6 TiO 2 O 24 corresponds. Recent studies have shown that antimony is present in two different valencies and occupies two different positions in the Lewisite . Crystal structure studies have also shown that Lewisite is identical to Hydroxycalcioroméite.

Six microprobe analyzes on Lewisite grains from the type locality yielded mean values ​​of 0.90% Na 2 O; 12.80% CaO; 1.64% MnO; 4.43% Fe 2 O 3 ; 1.70% Al 2 O 3 ; 14.47% TiO 2 ; 64.66% Sb 2 O 5 ; 0.65% SO 3 and total = 101.25%. On the basis of two cations on the B position per formula unit, the empirical formula (Ca 0.91 , Sb 3+ 0.27 , Fe 0.19 , Al 0.10 , Na 0.10 , Mn 0.06 ) (Sb 5+ 1.28 , Ti 0.72 ) O 6 (OH) calculated, resulting in (Ca, Sb 3+ , Fe3 +, Al, Na, Mn, □) 2 (Sb 5+ , Ti) 2 O 6 (OH) has been simplified.

The assumption of the formula (Ca 0.75 Sb 3+ 0.25 ) 2 (Sb 5+ 0.75 Ti 0.25 ) 2 O 6 (OH), in which a quarter of the A or B position of actually non-formula elements is occupied, requires a content of 0.23 wt .-% hydrogen; 25.42 wt% oxygen; 13.65 wt% calcium; 5.43 wt% titanium and 55.27 wt% antimony.

Hydroxycalcioroméite is the only mineral with the element combination Ca - Sb - H - O. In addition to the closely related minerals fluorcalcioroméite and oxycalcioroméite etc., they are chemically similar a. the inadequately characterized phases mauceliite , (Pb, Ca, Na) 2 (Sb, Ti) 2 (O, OH, F) 7 ; Scheteligit , (Ca, Fe, Mn, Sb, Bi, Y) 2 (Ti, Ta, Nb, W) 2 (O, OH) 7 ; as well as the as yet unnamed Sb analogue of hydroxymanganopyrochlore, (Mn, Ca, Y) 2 (Sb, Ti) 2 O 6 (OH).

Within the pyrochlore upper group there are theoretically a multitude of substitution possibilities due to the four different positions to be occupied. Within the Roméit group, hydroxycalcioroméite is the OH-dominant analogue to the F-dominated fluorcalcioroméite and to the O-dominated oxycalcioroméite as well as the Ca-dominant analogue to the Fe-dominated hydroxyferroroméite. Across all subgroups, hydroxycalcioroméit is the Sb-dominant analogue of the Ta-dominated hydroxycalciomicrolite and the Nb-dominated hydroxycalciopyrochloride.

Crystal structure

Hydroxycalcioroméit crystallizes in the cubic crystal system in the space group Fd 3 m (space group no. 227) with the lattice parameter a = 10.264  Å and eight formula units per unit cell . Natalia Zubkova and colleagues determined a lattice parameter a = 10.311 Å. Template: room group / 227

properties

morphology

Hydroxycalcioroméit was found at its type locality only within a heavy mineral concentrate. It occurred here in the form of crystals up to 1 mm in size, whose costume consists exclusively of the octahedron {111} without any modifying shapes. Twins according to (111) are rare. Under the microscope, colorless, birefringent grains and flakes of mica are found in some of the crystals, some of which extend beyond the surfaces of the Lewisite crystals, as well as very fine yellow needles (rutile?) And isolated gas pores. The Lewisite crystals are occasionally covered with a sulfur-yellow decomposition bark. Lewisite from the Johnny Lyon Hills in Arizona, USA, has been described in the form of superficially transformed (altered) or completely pseudomorphosed large tetrahedron crystals. Furthermore in earthy masses.

physical and chemical properties

The crystals of the hydroxycalcioroméite are honey yellow to colophony brown, amber yellow, golden yellow or yellow brown and orange brown, while their line color is always light yellowish brown. The surfaces of the translucent to transparent Hydroxycalcioroméits show a glassy to resinous gloss . There is no information on the refraction of light. Hydroxycalcioroméit has no birefringence because it belongs to the cubic crystal system and is optically completely isotropic. Under the microscope , the mineral shows no pleochroism

Hydroxycalcioroméite has a perfect cleavage after the octahedron {111}. Due to its brittleness , it breaks like quartz , with the fracture surfaces being (semi) shell-shaped. According to the original description, the mineral is "not brittle". With a Mohs hardness of 5.5, the mineral is one of the medium-hard minerals and, like the reference minerals apatite (hardness 5), can be scratched with a pocket knife and orthoclase (hardness 6) with a steel file. The measured density for hydroxycalcioroméit is 4.956 g / cm³, the calculated density is 4.73 g / cm³, 4.966 g / cm³ and 5.31 g / cm³, depending on the author. Hydroxycalcioroméit is neither in the long wavelength even in the short wavelength UV light , a fluorescent .

In the Bunsen flame , Lewisite can be melted fairly easily at the edges, whereby a greenish- blue flame color can be recognized at the same time . The phosphorus salt pearl is hot violet, cold yellow in the reduction flame. The mineral is insoluble in acids , but can be decomposed by melting with sodium carbonate . It is slightly reduced when heated in hydrogen to a mild red heat .

Education and Locations

Hydroxycalcioroméite ( Lewisite ) was found in a heavy mineral concentrate which occurs in a gravel resulting from the decomposition of mica schist.

Typical accompanying minerals of Hydroxycalcioroméits in its type material, in addition to Cinnabarit still wine yellow xenotime (Y) , light sulfur-yellow and yellowish brown monazite , wine yellow zircon , colorless to dark gray kyanite , dark brown tourmaline , rutile , hematite , pyrite , magnetite , solid gold and Derbylit .

As a rare mineral formation, the hydroxycalcioroméite could only be described from around fifteen sites so far (as of 2018). The type locality for hydroxycalcioroméit is the cinnabarite mine "Fazenda Tres Cruzes" near Tripuí (formerly Tripuhy) in the Ouro-Preto district near Ouro Preto , Minas Gerais in Brazil .

Further findings are:

Sites for Hydroxycalcioroméit from Germany and Switzerland are therefore unknown.

See also

literature

  • 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 May 2, 2020]).
  • Roland C. Rouse, Pete J. Dunn, Donald R. Peacor, Liping Wang: Structural studies of the natural antimonian pyrochlores. I. Mixed valency, cation site splitting, and symmetry reduction in lewisite . In: Journal of Solid State Chemistry . tape 141 , no. 2 , 1998, p. 562-569 , doi : 10.1006 / jssc.1998.8019 (English).
  • Natalia V. Zubkova, Dmitry Yu. Pushcharovsky, Daniel Atencio, Alla V. Arakcheeva, Paulo Anselmo Matioli: The crystal structure of lewisite, (Ca, Sb 3+ , Fe 3+ , Al, Na, Mn, □) 2 (Sb 5+ , Ti) 2 O 6 (OH) . In: Journal of Alloys and Compounds . tape 296 , no. 1-2 , 2000, pp. 562-569 , doi : 10.1016 / S0925-8388 (99) 00513-7 (English).
  • Lewisite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 66 kB ; accessed on November 13, 2018]).

Web links

Individual evidence

  1. ↑ Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2020, accessed May 2, 2020 .
  2. ↑ a b c d e f g h i j k l m n o p q r s Hydroxycalcioroméite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 2, 2020 .
  3. ↑ a b c d e f g Natalia V. Zubkova, Dmitry Yu. Pushcharovsky, Daniel Atencio, Alla V. Arakcheeva, Paulo Anselmo Matioli: The crystal structure of lewisite, (Ca, Sb 3+ , Fe 3+ , Al, Na, Mn, □) 2 (Sb 5+ , Ti) 2 O 6 (OH) . In: Journal of Alloys and Compounds . tape 296 , no. 1-2 , 2000, pp. 562-569 , doi : 10.1016 / S0925-8388 (99) 00513-7 (English).
  4. ↑ a b c d e Lewisite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 66  kB ; accessed on November 13, 2018]).
  5. ↑ 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 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 May 2, 2020]).
  6. ^ A b c d e Roland C. Rouse, Pete J. Dunn, Donald R. Peacor, Liping Wang: Structural studies of the natural antimonian pyrochlores. I. Mixed valency, cation site splitting, and symmetry reduction in lewisite . In: Journal of Solid State Chemistry . tape 141 , no. 2 , 1998, p. 562-569 , doi : 10.1006 / jssc.1998.8019 (English).
  7. ^ Wilhelm Ludwig von Eschwege : Pluto Brasiliensis . A series of treatises on Brazil's gold, diamond and other mineral wealth, the history of its discovery, the occurrence of its deposits, the operation, the yield and the related legislation, etc. G. Reimer, Berlin 1833, p.  456–457 ( limited preview in Google Book Search [accessed November 13, 2018]).
  8. ↑ Ernst AJ Burke: A mass discreditation of GQN minerals . In: The Canadian Mineralogist . tape 44 , 2006, pp. 1557–1560 , doi : 10.3749 / canmin.48.3.673 (English, rruff.info [PDF; 116 kB ; accessed on November 13, 2018]).
  9. ^ Donald David Hogarth: Classification and nomenclature of the pyrochlore group . In: The American Mineralogist . tape 62 , 1977, pp. 403-410 (English, rruff.info [PDF; 849 kB ; accessed on May 2, 2020]).
  10. ↑ a b c d e f 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]).
  11. ^ A b c d Andrew G. Christy, Daniel Atencio: Clarification of 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; 85 kB ; accessed on August 30, 2018]).
  12. ^ Hydroxycalcioroméit. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on May 2, 2020 .
  13. ^ 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]).
  14. ↑ 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).
  15. ↑ Stuart J. Mills, Andrew G. Christy, Mike S. Rumsey, John Spratt, Erica Bittarello, Georges Favreau, Marco E. Ciriotti, Christian Berbain: Hydroxyferroroméite, a new secondary weathering mineral from Oms, France . In: European Journal of Mineralogy . tape 29 , no. 2 , 2017, p. 307–314 , doi : 10.1127 / ejm / 2017 / 0029-2594 (English).
  16. ↑ 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).
  17. ↑ 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).
  18. ↑ Localities for Hydroxycalcioroméite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 2, 2020 .
  19. ↑ Find location list for Hydroxycalcioroméite at the Mineralienatlas and at Mindat (accessed on November 13, 2018)