Cabalzarit

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Cabalzarit
Cabalzarite-459635.jpg
Cabalzarite from the "Falotta Pit" near Tinizong (Tinzen), Canton of Graubünden, Switzerland (field of view 4 mm)
General and classification
other names

IMA 1997-012

chemical formula
  • CaMg 2 (AsO 4 ) 2 · 2H 2 O
  • Ca (Mg, Al, Fe) 2 (AsO 4 ) 2 (H 2 O, OH) 2
  • Ca (Mg, Al, Fe 2+ ) 2 [(H 2 O, OH) | AsO 4 ] 2
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.CG.15 ( 8th edition : VII / C.31)
02/40/12/01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 8.925  Å ; b  = 6.143 Å; c  = 7.352 Å
β  = 115.25 °
Formula units Z  = 2
Frequent crystal faces {001} as well as a prism and two more pinacoids
Twinning no
Physical Properties
Mohs hardness ≈ 5, VHN 50  = 429 kg / mm 2
Density (g / cm 3 ) 3.89 (measured); 3.64-3.86 (calculated)
Cleavage no
Break ; Tenacity uneven; not specified
colour light brownish to brownish-pink, rarely orange-brown
Line color colorless, i.e. white
transparency transparent
shine Glass gloss
Crystal optics
Refractive index n  = 1.76 (parallel to fiber elongation); 1.70 (perpendicular to fiber elongation); 1.77 (calculated)
Optical character biaxial

Cabalzarit is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition Ca (Mg, Al, Fe) 2 (AsO 4 ) 2 (H 2 O, OH) 2 and is therefore chemically a water-containing calcium - magnesium - aluminum - iron - arsenate with a variable Proportion of additional hydroxide ions .

At its type locality, Cabalzarit develops isolated crystals, 1 mm in size, with often curved surfaces and ax-shaped habit, sitting in corridors in the brownite ore . In addition, there are complex polycrystalline aggregates with a maximum length of 2 mm, radial-ray aggregates of fibrous to tabular crystals of 3 mm in length, and parallel-fiber aggregates that completely fill ducts up to 2 mm thick. The type locality of the mineral is the former manganese deposit of the "Grube Falotta" located 14.3 km south-southeast of Tiefencastel near Tinizong (Tinzen), Oberhalbstein in the Albula Valley , Graubünden , Switzerland .

Etymology and history

The heaps of abandoned "mine Falotta" in Oberhalbstein known for interesting arsenic minerals occurring in Gängchen massive brandtite - Sarkinit with subordinate Manganberzeliit and Grischunit as well as in small, open fractures occurring, free-standing crystals of Tilasit , Kemmlitzit , Bergslagit and Geigerit . Here, in the mid-1990s, Swiss mineral collectors discovered a visually unidentifiable mineral that was suspected to be another new mineral phase. The Swiss mineral collector Thomas Mummentaler (Zurich), Hans-Peter Klinger (Jonah) and Walter Cabalzar (Chur) presented material available in the mineralogist at the Institute of Crystallography of the University of Lausanne and at the Institute for Mineralogy and Petrology of the University of Basel a new representative of the Tsumcorite group recognized. After extensive research, the new phase was presented to the International Mineralogical Association (IMA), which recognized it as a new mineral in 1997. In 2000, an international team of scientists led by the Swiss-Australian mineralogist Joël Brugger and Nicolas Meisser , Kurt Schenk, Peter Berlepsch , Michel Bonin, Thomas Armbruster , Daniel Nyfeler and Susanne Schmidt in the US science magazine "The American Mineralogist" as Cabalzarit described. The authors named the mineral after the Swiss amateur mineralogist Walter Cabalzar (* 1919) in recognition of his contributions to the mineralogy of the Canton of Graubünden. Cabalzar was u. a. involved in the discovery of the two minerals Grischunit and Geigerit, whose type locality in both cases is also the “Falotta mine”.

The type material for Cabalzarit is kept under the catalog numbers MGL # 73785 and # MGL 73786 (holotype) as well as MGL # 65185 and MGL # 73787 (cotype) in the "Collection of the Musée cantonal de géologie de Lausanne" in Lausanne , Switzerland. Another Cotyp level is in the collection of the Natural History Museum Basel (catalog number 13002).

classification

The current classification of the International Mineralogical Association (IMA) counts the Cabalzarite to the tsumcorite group with the general formula Me (1) Me (2) 2 (XO 4 ) 2 (OH, H 2 O) 2 , in which Me (1), Me (2) and X different positions in the structure of the minerals of the tsumcorite group with Me (1) = Pb 2+ , Ca 2+ , Na + , K + and Bi 3+ ; Me (2) = Fe 3+ , Mn 3+ , Cu 2+ , Zn 2+ , Co 2+ , Ni 2+ , Mg 2+ and Al 3+ and X = As 5+ , P 5+ , V 5+ and represent S 6+ . To Tsumcoritgruppe include not only Cabalzarit still Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Kaliochalcit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite . Cabalzarite forms together with cobalt solder armyerite ( Me (2) = Co), ferrilotharmeyerite (Fe 3+ ), lotharmeyerite (Zn), manganese solder armyerite (Mn) and nickellotharmeyerite (Ni) the "Lotharmeyerite subgroup".

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the cabalzarite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where together with cobalt solder armeyerite, cobalt sumcorite, ferrilotharmeyerite , Gartrellite, Helmutwinklerit, Krettnichit, Lotharmeyerit, Lukrahnit, Manganlotharmeyerit, Mawbyit, Mounanait, Nickellotharmeyerit, Nickelschneebergit, Phosphogartrellite, Rappoldit, Schneebergit, Thometzekit, Tsumcorit and zinc gartrellite-group "Tsumcorit-Nr." VII / C.31 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 Cabalzarit to the category of “phosphates, etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex to the water of crystallization content , so that the mineral can be classified according to its composition in the subsection “With large and medium-sized cations; RO 4  : H 2 O = 1: 1 "is to be found, where together with cobalt solder armeyerite, cobalt sumcorite, ferrilotharmeyerite, krettnichite, lotharmeyerite, manganese solder armyerite, mawbyite, mounanaite, nickelotharmeyerite, nickel snow mountainite, snow mountainite", thometzekite and tsumcorite with the tsumcorite group System no. 8.CG.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Cabalzarit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates etc.". Here he is to be found as the only member in the unnamed group 02/40/12 within the sub-section “ Water-containing phosphates etc., with A 2+ (B 2+ ) 2 (XO 4 ) × x (H 2 O) ”.

Chemism

Four microprobe analyzes on Cabalzarit resulted in mean values ​​of 13.64% CaO; 7.54 MgO; 0.49% SrO; 9.84% Al 2 O 3 ; 0.55% Mn 2 O 3 ; 4.38% Fe 2 O 3 ; 0.05% SiO 2 ; 55.57% As 2 O 5 and 7.11% H 2 O (calculated) as well as small amounts of V 2 O 5 (≤ 0.15%), P 2 O 5 (≤ 0.11%), Na 2 O (≤ 0.08%) and PbO (≤ 0.12%). On the basis of ten oxygen atoms , the empirical formula (Ca 1.00 , Sr 0.02 ) Σ = 1.02 (Al 0.80 Mg 0.77 Fe 0.23 Mn 0.03 ) Σ = 1 was calculated from them , 83 (AsO 4 ) 2 [(H 2 O) 1.24 (OH) 0.76 ] Σ = 2.00 , which Ca (Al, Mg, Fe 3+ ) (AsO 4 ) 2 (H 2 O , OH) 2 was idealized.

The chemical variability of the cabalzarite crystals takes place primarily on the Me (2) position with the inclusion of Mg, Al, Fe and - to a much lesser extent - Mn. In a Mg-Fe-Al triangular diagram, the points representing the composition are almost evenly distributed between the Mg and Al fields and are partially close to the triple point . As a result, mixed crystal formation on the Me (2) position is widespread in the crystals with the inclusion of the di- and trivalent elements mentioned. The mixed crystal formation on the Me (2) position is accompanied by a coupled substitution according to M 2+ + H 2 O ↔ M 3+ + OH - .

Cabalzarite is a typical example of a mineral with a nomenclature classification problem because its chemical composition lies in the middle of a row of mixed crystals. Crystals with dominance of Mg 2+ as well as Al 3+ are found on the Me (2) position, the Al / Mg ratio varies between 0.69 and 2.21. The majority of the analyzes lie on both sides of the line Al: Mg = 1: 1. Also, no crystal with Al or Mg terminated link composition could be isolated. In accordance with the guidelines of the IMA, no two different names were given for the two theoretical end members, but only one name for the real intermediate mixed crystal .

Cabalzarite represents the Mg-dominant analogue to the Zn-dominated Lotharmeyerite. It is also the corresponding analogue to the Fe 3+ -dominated Ferrilotharmeyerite, to the Mn 3+ -dominated manganese solderarmyerite, to the co-dominated cobalt solderarmyerite and to the Ni-dominated nickel solderarmyerite.

Crystal structure

Cabalzarite crystallizes in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 8.925  Å ; b  = 6.143 Å; c  = 7.352 Å and β = 115.25 as well as two formula units per unit cell . Template: room group / 12

The crystal structure of Cabalzarite is identical to the structure of the other representatives of the tsumcorite group. The Me (2) Φ 6 - octahedra (Φ: O 2− , OH - , H 2 O) have common edges and are arranged as chains stretched in the direction of the b-axis [010]. These chains are shared by corners with AsO 4 - tetrahedra linked to each other, thereby forming layers having the composition Me (2) (AsO 4 ) (OH, H 2 O), which are arranged in parallel (001). The topology of this layer is identical to that in natrochalcite, NaCu 2 (SO 4 ) 2 (H 3 O 2 ). The Ca 2+ cations are located between the layers and ensure the connection between the layers in the direction of the a-axis [100]. Hydrogen bonds exist in the layers (between the two O1 atoms that belong to two octahedron chains) and across the layers (between O1 and O4 at the tip of the AsO 4 tetrahedron). The structures of cabalzarite and ferrilotharmeyerite are very similar; the main difference between the two is the size of the Me (2) octahedron.

Cabalzarite is isotypic (isostructural) to the monoclinic representatives of the tsumcorite group such as tsumcorite and natrochalcite and the other above-mentioned representatives of the Lotharmeyerite subgroup.

properties

morphology

At its type locality, Cabalzarit develops single crystals with a maximum size of 1 mm, which have an axinite-like habit and often curved surfaces. They are flat-shaped after the basic pinaloid {001} and have the surfaces of a prism and two further pinacoids . There are also fibrous to tabular crystals up to 3 mm in length, which are grouped into radial aggregates up to 5 mm in diameter. They sit in thin cracks and are developed in two dimensions, but if there is enough space for crystallization, they also form three-dimensional, spherical aggregates. Cabalzarite can also be found in the form of complex polycrystalline aggregates up to 2 mm in length sitting in druses and in parallel-fiber aggregates that fill 2 mm thick corridors. Cabalzarite aggregates with this formation can be confused with the silicate mineral sursassite , which occurs in their paragenesis.

physical and chemical properties

The crystals of Cabalzarit are light brownish to brownish-pink, rarely orange-brown. The line color of the Cabalzarite is indicated as colorless, but since there can be no colorless mineral powder, it is probably white. The surfaces of the transparent crystals have a glass-like sheen , which agrees well with the values ​​for light refraction . Medium to high values ​​for light refraction (n = 1.76 parallel to the fiber elongation, n = 1.70 perpendicular to it) and for birefringence (δ = 0.060) were found on the crystals of Cabalzarite . The calculated value for the refraction is 1.77. Under the microscope , the mineral shows no pleochroism in transmitted light .

Cabalzarite has no cleavage . But it breaks like amblygonite , with the fracture surfaces being uneven. With a Mohs hardness of ≈ 5, the mineral is one of the medium-hard minerals, so it stands between the reference minerals fluorite (hardness 4) and apatite (hardness 5) and, like these, can be easily scratched with a pocket knife more (fluorite) or less (apatite). The Vickers hardness VHN 50 was determined to be 429 kg / mm 2 . The measured density for Cabalzarite is 3.89 g / cm 3 , the calculated density 3.64-3.86 g / cm 3 . The mineral is neither in the long term nor in the short wavelength UV light , a fluorescent .

There is no information on the chemical behavior, especially towards acids.

Education and Locations

Cabalzarit is a typical secondary mineral , which, Manganlotharmeyerit, but similar in contrast to most other representatives of Tsumcoritgruppe, not in the oxidation zone of arsenic-rich polymetallic non-ferrous metal - deposits , but metamorphosed retrograde , syngeneic - exhalative manganese ores was discovered. The sedimentary ores recrystallized during the regional Alpine metamorphism under the lowest green slate facial conditions (≤ 325 ° C, 3–5 kb). Today the ores consist mainly of Braunite , Rhodonite and Spessartine , in addition locally tinzenite , Parsettensite , Sursassite and a strontium-containing Piedmontite .

As a very rare mineral formation, Cabalzarite could only be described from three sites so far (as of 2018). The type locality of Cabalzarit is the small manganese deposit of the "Falotta mine" near Tinizong (Tinzen), Oberhalbstein in the Albula valley , Graubünden , Switzerland , from which approx. 1800 t of manganese ore were extracted during the Second World War from 1941 to 1945. Falotta is one of the countless small manganese deposits located in radiolarites from the Upper Jura (Malm), which overlay the MORB basalts within the mighty ophiolithic sequence of the tectonic plate ceiling in the Swiss Alps.

Interestingly, the mineral was also found in non-ferrous metal deposits. These include the “Aghbar Mine” and the Aghbar open-cast mine in the mining area of ​​Bou Azzer near Taznakht (Tazenakht), Ouarzazate province in the Drâa-Tafilalet region in southern Morocco , where the mineral was produced as a result of the weathering of a Variscan hydrothermal Co-Ni-As - (Cu-U-Mo) - Gangs came into being. Cabalzarite is found here in tiny yellowish grains together with arseniosiderite in the matrix of erythrin - talmessite - steps on which gypsum-like Maghrebit crystals sit.

The third place where Cabalzarite was found turned out to be the "Miniera di Monte Nero" near Rocchetta di Vara not far from La Spezia , Liguria region in Italy.

Paragenesis minerals of Cabalzarits in the pit "Falotta" are quartz , "Adular" , Kutnahorit , Tilasit , Grischunit and Arseniosiderit along with fine needle aggregates of Tripuhyite , black crusts from Manganoxihydroxiden ( Rancieit - Takanelit ) and pseudorhomboedrischen Arsenogoyazitkristallen . In the Aghbar opencast mine in the Bou Azzer district, cabalzarite is accompanied by quartz, erythrin, arseniosiderite and wendwilsonite .

Occurrences of Cabalzarite in Germany , Austria or Switzerland are therefore not known.

use

Due to its rarity, Cabalzarite is only of interest to mineral collectors.

See also

literature

  • Joël Brugger, Nicolas Meisser, Kurt Schenk, Peter Berlepsch, Michel Bonin, Thomas Armbruster, Daniel Nyfeler and Susanne Schmidt: Description and crystal structure of cabalzarite Ca (Mg, Al, Fe) 2 (AsO 4 ) 2 (H 2 O, OH ) 2 , a new mineral from the tsumcorite group . In: The American Mineralogist . tape 85 , no. 12 , 2000, pp. 1307-1314 , doi : 10.2138 / am-2000-8-925 ( rruff.info [PDF; 627 kB ; accessed on May 18, 2018]).
  • Joseph A. Mandarino: New minerals . In: The Canadian Mineralogist . tape 40 , no. 1 , 2002, p. 249 , doi : 10.2113 / gscanmin.40.1.247 ( rruff.info [PDF; 108 kB ; accessed on May 18, 2018]).
  • Philippe Roth: Minerals first discovered in Switzerland and minerals named after Swiss individuals . 1st edition. Kristallografik Verlag, Achberg 2007, ISBN 978-3-9807561-8-1 , p. 104-105 .

Web links

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

Individual evidence

  1. ^ IMA / CNMNC List of Mineral Names; March 2018 ( Memento from June 11, 2018 in the Internet Archive ) (PDF 1.65 MB)
  2. ↑ 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 Joël Brugger, Nicolas Meisser, Kurt Schenk, Peter Berlepsch, Michel Bonin, Thomas Armbruster, Daniel Nyfeler and Susanne Schmidt: Description and crystal structure of cabalzarite Ca (Mg, Al, Fe) 2 (AsO 4 ) 2 (H 2 O, OH) 2 , a new mineral of the tsumcorite group . In: The American Mineralogist . tape 85 , no. 12 , 2000, pp. 1307-1314 , doi : 10.2138 / am-2000-8-925 ( rruff.info [PDF; 627 kB ; accessed on May 18, 2018]).
  3. ^ 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.  730 .
  4. ^ Philippe Roth: Minerals first discovered in Switzerland and minerals named after Swiss individuals . 1st edition. Kristallografik Verlag, Achberg 2007, ISBN 978-3-9807561-8-1 , p. 46-47 .
  5. ↑ Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger, Werner Mikenda: Crystal chemistry of the tsumcorite-group minerals. New data on ferrilotharmeyerite, tsumcorite, thometzekite, mounanaite, helmutwinklerite, and a redefinition of gartrellite . In: European Journal of Mineralogy . tape 10 , 1998, pp. 179-206 , doi : 10.1127 / ejm / 10/2/0179 .
  6. ↑ Ernest H. Nickel: Solid solutions in mineral nomenclature . In: Mineralogical Magazine . tape 56 , 1992, pp. 127–130 ( minersoc.org [PDF; 197 kB ; accessed on May 18, 2018]).
  7. ↑ Ernest H. Nickel: Nomenclature for mineral solid solutions . In: The American Mineralogist . tape 77 , no. 5/6 , 1992, pp. 660–662 ( rruff.info [PDF; 269 kB ; accessed on May 18, 2018]).
  8. ↑ a b Mindat - Cabalzarit
  9. ↑ Joël Brugger, Sergey V. Krivovichev, Uwe Kolitsch, Nicolas Meisser, Michael Andrut, Stefan Ansermet, Peter C. Burns: Description and crystal structure of manganlotharmeyerite, Ca (Mn 3+ , ◻, Mg) 2 {AsO 4 , [AsO 2 (OH) 2 ]} 2 (OH, H 2 O) 2 from the Starlera Mn deposit, Swiss Alps, and a redefinition of lotharmeyerite . In: The Canadian Mineralogist . tape 40 , no. 4 , 2002, p. 1597–1608 , doi : 10.2113 / gscanmin.40.6.1597 ( rruff.info [PDF; 1.1 MB ; accessed on February 20, 2018]).
  10. ↑ Mindat - Number of localities for Cabalzarit
  11. ↑ a b c List of localities for Cabalzarite at the Mineralienatlas and at Mindat
  12. ↑ Mindat - Falotta Pit
  13. ↑ Georges Favreau, Jacques Emile Dietrich, Nicolas Meisser, Joël Brugger, Lahcen Ait Haddouch, Lhou Maacha: Famous Mineral Localities: Bou Azzer, Morocco . In: The Mineralogical Record . tape 38 , no. 5 , 2007, p. 363 ( researchgate.net [PDF; 22.8 MB ; accessed on May 18, 2018]).
  14. ↑ Nicolas Meisser, Joël Brugger: Bouazzerite and Maghrebit, two new arsenate minerals from the Bou Azzer district, Morocco . In: Lapis . tape 31 , no. 7/8 , 2006, pp. 69-71 .
  15. ↑ Nicolas Meisser, Joël Brugger, Sergey Krivovichev, Thomas Armbruster, Georges Favreau: Description and crystal structure of maghrebite, MgAl 2 (AsO 4 ) 2 (OH) 2 · 8H 2 O, from Aghbar, Anti-Atlas, Morocco: first arsenate in the laueite mineral group . In: European Journal of Mineralogy . tape 24 , 2012, p. 717-726 , doi : 10.1127 / 0935-1221 / 2012 / 0024-2172 .