Cobalt solder armyerite

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Cobalt solder armyerite
Cobaltlotharmeyerite-120475.jpg
Brown cobalt solder armyerite crystal aggregates from the Aghbar mine near Aghbar, Bou Azzer District, Tazenakht, Ouarzazate Province, Souss-Massa-Draâ Region, Morocco (field of view: 3 mm)
General and classification
other names

IMA 1997-027

chemical formula
  • Ca (Co, Fe, Ni) 2 (AsO 4 ) 2 (OH, H 2 O) 2
  • Ca (Co, Fe 3+ ) 2 [(OH, H 2 O) 2 | (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)
01/37/06/03
Similar minerals Lotharmeyerite, manganese solderarmyerite
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  = 9.024  Å ; b  = 6.230 Å; c  = 7.421 Å
β  = 115.15 °
Formula units Z  = 2
Frequent crystal faces { 1 01}, {102}, {111}
Physical Properties
Mohs hardness 4.5
Density (g / cm 3 ) 4.13 (calculated)
Cleavage no
Break ; Tenacity not specified; not specified
colour brown
Line color light brown
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.78
n β  = 1.79
n γ  = 1.85
Birefringence δ = 0.070
Optical character biaxial positive
Axis angle 2V = 48 ° (measured); 2V = 46 ° (calculated)
Pleochroism strong from X = yellow to Y = brown to Z = pale yellow
Other properties
Chemical behavior slowly soluble in warm, dilute hydrochloric acid without effervescence

Cobalt solder armyerite 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 (Co, Fe, Ni) 2 (AsO 4 ) 2 (OH, H 2 O) 2 and is therefore chemically a water-containing calcium - cobalt - iron - nickel - arsenate with a variable Proportion of additional hydroxide ions .

Cobalt solder armyerite develops latte crystals at its type locality , which have grown together to form fan-shaped aggregates , as well as microcrystalline crusts. Also described are aggregates of very small (<20 µm) cobalt solder armyerite crystals, which often form lattice-like frameworks 50-100 µm thick and a few centimeters long, which consist of perpendicularly arranged crystals and obviously represent pseudomorphoses after skutterudite and / or nickel cutterudite . The type locality of the mineral are heaps in the mining district "Am Roten Berg", 4.8 km southwest of the city center of Schneeberg in the Saxon Ore Mountains , where hematite ore was mined in earlier times .

Etymology and history

Julius Lothar von Meyer - namesake for Lotharmeyerite and the related cobaltlotharmeyerite

In the second half of the 1990s, several representatives of the tsumcorite group were discovered in the area of ​​the old iron stone mine on the Rote Berg in Schneeberg, whose differentiation by external characteristics was practically impossible. X-ray diffractometric examinations provided almost identical diagrams and the EDX analyzes only allowed clear statements to be made in some cases. In most cases, reliable assignments are only possible using microprobe analyzes in the wavelength-dispersive mode . As a result, extensive research was required before the International Mineralogical Association (IMA) could be presented with a new mineral phase, which it recognized in 1997. In 1999 the mineral was described by an international team of scientists led by the German chemist Werner Krause as well as Herta Effenberger , Heinz-Jürgen Bernhardt and Mirko Martin in the German science magazine “New Yearbook for Mineralogy, Monthly Books” as cobalt solder armyerite. The authors named the mineral because of its relationship with Lotharmeyerite and the dominance of cobalt on the Me (2) position.

The type material for cobalt solder armyerite is stored under catalog numbers 79273 (holotype) and 79274 (cotype) at location "c 7.5" in the mineralogical collection of the Technical University Bergakademie Freiberg in Freiberg , Germany.

classification

The current classification of the International Mineralogical Association (IMA) counts cobalt solder armyerite 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 Cobaltlotharmeyerit still Cabalzarit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Kaliochalcit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite . Together with Lotharmeyerite ( Me (2) = Zn), Cabalzarite (Mg), Ferrilotharmeyerite (Fe 3+ ), Manganese Solotharmeyerite (Mn) and Nickellotharmeyerite (Ni), cobalt solder armyerite forms the "Lotharmeyerite subgroup".

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the cobaltotharmeyerite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates without foreign anions ", where it belongs together with cabalzarite, cobalt sumcorite, ferrilotharmeyerite , Gartrellite, Helmutwinklerit, Krettnichit, Lotharmeyerit, Lukrahnit, Manganlotharmeyerit, Mawbyit, Mounanait, Nickellotharmeyerit, Nickelschneebergit, Phosphogartrellite, Rappoldit, Schneebergite, Thometzekit, Tsumcorit and Zincgartrellite-Nr. Gartrellit-Group "Tsumcorit" 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 cobalt solder armyerite 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 cabalzarite, cobalt sumcorite, ferrilotharmeyerite, krettnichite, lotharmeyerite, manganese solderarmyerite, mawbyite, mounanaite, nickellotharmeyerite, nickel snow mountainite, snow mountainite", Thometzekit and tsumcorite group "tsumcorite System no. 8.CG.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns cobalt solder armyerite to the class of "phosphates, arsenates and vanadates" and there to the department of "phosphate minerals". Here it is together with Lotharmeyerite, Ferrilotharmeyerite and Nickellotharmeyerite in the " Lotharmeyerite series " with the system no. 37.01.06 to be found in the subsection of "Anhydrous acidic phosphates etc., with various formulas".

Chemism

Sixteen microprobe analyzes on cobalt solder armyerite resulted in mean values ​​of 12.18% CaO; 5.76% NiO; 15.70% CoO; 11.53% Fe 2 O 3 ; 49.36% As 2 O 5 and 6.39% H 2 O (calculated) as well as smaller amounts (<0.05% by weight) of CuO, PbO, Bi 2 O 3 and SO 3 . Based on ten oxygen atoms , the empirical formula Ca 1.01 (Co 0.97 Fe 3+ 0.67 Ni 0.36 ) Σ = 2.00 (AsO 4 ) 2.00 · [(OH) 0.69 (H 2 O) 1.31 ] Σ = 2.00 , which was idealized to Ca (Co, Fe 3+ , Ni) (AsO 4 ) 2 (OH, H 2 O) 2 . Solid solution formation involving Co, Fe 3+ and Ni is widespread in the crystals . The Fe / Ni ratio in cobalt solder armeyerite is mostly> 1, but crystals with Fe / Ni <1 were also found. The charge balance is achieved by heterovalent exchange mechanisms with a coupled substitution involving OH / H 2 O groups according to the following scheme: [(Co, Ni) 2+ (H 2 O)] 2+ ↔ [Fe 3+ (OH) - ] 2+ .

The substitution of Ca by Bi 3+ is of particular interest , with the highest measured contents amounting to 19% by weight Bi 2 O 3 . Cobalt solder armyerite was the first member of the tsumcorite group with a trivalent cation at the Me (1) position. Two exchange mechanisms involving divalent and trivalent cations on the Me (1) position lead to charge equalization: [Ca 2+ (H 2 O) 0 ] 2+ ↔ [Bi 3+ (OH) - ] 2+ and [ Ca 2+ Me (2) 3+ ] 5+ ↔ [Bi 3+ Me (2) 2+ ] 5+ . The second mechanism is supported by chemical analyzes, since Bi-containing representatives obviously contain less Fe 3+ than Bi-free samples. This compensates for the increased charge on the Me (1) position and results in a more or less unaffected OH / H 2 O ratio. The Bi end link Schneebergite with the formula Bi (Co, Ni) (AsO 4 ) 2 (OH, H 2 O) 2 is therefore free of iron.

Cobalt solder armyerite represents the co-dominant analogue to the Zn-dominated Lotharmeyerite. It is also the corresponding analogue to the Mg-dominated Cabalzarite, to the Fe 3+ -dominated ferrilotharmeyerite, to the Mn 3+ -dominated manganese solderarmyerite and to the Ni-dominated nickellotharmeyerite. Cobalt solder armyerite is also the Ca-dominated analogue of the Bi-dominated snow mountainite, with which it forms a complete series of mixed crystals .

Crystal structure

 Cobalt solder armyerite crystallizes in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with the lattice parameters a = 9.024  Å ; b  = 6.230 Å; c  = 7.421 Å and β = 115.15 ° as well as two formula units per unit cell . Template: room group / 12

The crystal structure of cobalt solder armyerite 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].

Cobalt lotharmeyerite 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

Cobalt solder armyerite develops in the material from the mine area “Am Roten Berg” thin-tabular, spear-shaped crystals with sizes <1 mm stretched along the b-axis [010], which come together to form millimeter-sized, fan-shaped to radial aggregates. They often form lattice-shaped frameworks made of small crystals arranged perpendicular to each other. These frameworks have dimensions of 50-100 µm thick and a few centimeters in length and obviously consist of pseudomorphoses of skutterudite and / or nickel cutterudite skeletal crystals. Even feather-like aggregated skeletal crystals of solid bismuth are pseudomorphosed by cobalt solder armyerite. The surface shapes { 1 01} and {102} can be identified on the crystals . The terminating faces in the spike-shaped end face area of ​​the crystals probably belong to the form {111}.

Cobalt solder armyerite crystals found on “Corridor 2” in Bou Azzer, Morocco in the early 1990s form free-standing, [010] elongated crystals that form tufted, spindle-shaped or lanceolate, sometimes rosette-shaped aggregates of approx. 0.1 mm in size meet. Rectangular appearing platelets also form spherical aggregates with a maximum diameter of 1 mm. Crystals recovered from the same passage in April / May 2002 represent the world's best representatives of this type of mineral and appear in the form of slightly convex leaflets that form either free-standing crystals or aggregates up to 3 mm in diameter. Hedgehog-shaped and leafy aggregates up to 0.5 mm are known from the "Aghbar opencast mine" in the Bou Azzer district.

physical and chemical properties

The crystals of cobalt solder armyerite are brown, but according to other information they can take on all brown tones (light brown, red brown, brown orange, dark brown red) depending on the crystal size and the occupation of the Me (2) position. Their line color , however, is always light brown. The surfaces of the transparent crystals have a glass-like sheen , which agrees well with the values ​​for light refraction . High values ​​for light refraction (n α  = 1.78; n β  = 1.79 n γ  = 1.85) and a very high value for birefringence (δ = 0.070) were identified in the crystals of coballotharmeyerite . Under the microscope , the mineral shows a strong pleochroism from X = yellow to Y = brown to Z = pale yellow in transmitted light .

Cobalt solder armyerite does not have any cleavage properties , information on breakage and tenacity is missing. With a Mohs hardness of 4.5, 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 calculated density for cobalt solder armyerite is 4.13 g / cm³. The mineral does not fluoresce in long or short-wave UV light .

Cobalt solder armyerite is only slowly soluble in warm, dilute hydrochloric acid , HCl, without effervescence.

Education and Locations

Cobaltlotharmeyerit is a typical secondary mineral , which as the most representative of Tsumcoritgruppe in the oxidation zone of arsenic-rich polymetallic non-ferrous metal - deposits formed. Decomposed anhydrite provided the calcium necessary for mineral formation, bismuth comes from the weathering of native bismuth, Co, Fe 3+ and Ni were provided by the dissolution of minerals of the skutterudite-nickel-cutterudite mixed crystal series.

The type locality of the cobalt solder armyerite is the mining area "Am Roten Berg" near Schneeberg, Ore Mountains , Saxony , Germany . Paragenesis minerals are yellow bariopharmacosiderite , arseniosiderite , oliveite , zeunerite , Co-containing mawbyite, tsumcorite, cobalt sumcorite, rooseveltite , waylandite , scorodite and quartz .

As a very rare mineral formation, cobalt solder armyerite has so far (as of 2018) only been described from ten sites in two locations. In addition to the type locality of the “Am Roten Berg” mine field, these are the “St. Daniel "," Rappold "," Güldener Falk "and" Sauschwart ", all in Schneeberg- Neustädtel , as well as the" Pucherschacht "in the Schneeberger mine field" Wolfgang Maaßen ". At the "Pucherschacht" cobalt solder armyerite is accompanied by ferrilotharmeyerite and nickellotharmeyerite, in the pit "Daniel" u. a. von Roselith , in the "Rappold" mine a. a. of cobalt sumorite.

The second site is the mining area of ​​Bou Azzer near Taznakht (Tazenakht), Ouarzazate province in the Drâa-Tafilalet region in southern Morocco . Cobalt solder armyerite was first found here in “Corridor 2” near Bou Azzer, where it is accompanied by roselite, “roselite-beta”, sphaerocobaltite , dolomite , cobalt austinite and picropharmacolite, as well as calcite and quartz. Also in the “Aghbar Mine” and in the Aghbar opencast mine, here together with pale pink dolomite, dark green cobalt austinite and cobalt-containing talmessite as well as with erythrin , wendwilsonite and mansfieldite . Finally also from the "Gang No. 52 ”in Aït Ahmane - here as a manganese-containing variety together with talmessite.

There are no known occurrences of cobalt solder armyerite in Austria or Switzerland .

use

Because of its rarity, cobalt solder armeyerite is only of interest to mineral collectors.

See also

literature

  • Werner Krause, Herta Effenberger, Heinz-Jürgen Bernhardt, Mirko Martin: Cobaltlotharmeyerite, Ca (Co, Fe, Ni) 2 (AsO 4 ) 2 (OH, H 2 O) 2 , a new mineral from Schneeberg, Germany . In: New yearbook for mineralogy, monthly books . tape 1999 , no. 11 , 1999, p. 505-517 .

Web links

Commons : Cobaltlotharmeyerite  - 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 Werner Krause, Herta Effenberger, Heinz-Jürgen Bernhardt, Mirko Martin: Cobaltlotharmeyerite, Ca ( Co, Fe, Ni) 2 (AsO 4 ) 2 (OH, H 2 O) 2 , a new mineral from Schneeberg, Germany . In: New yearbook for mineralogy, monthly books . tape 1999 , no. 11 , 1999, p. 505-517 .
  2. ^ 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.  485 .
  3. ↑ a b c Mindat - cobalt solder armyerite
  4. ↑ a b c Fritz Schlegel: New finds from the mountain area Schneeberg / Saxony, 1995–99 (I) . In: Lapis . tape 25 , no. 2 , 2000, pp. 31-38 .
  5. ↑ Type mineral catalog Germany - storage of the holotype and co-type level cobalt solder armyerite
  6. ↑ 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 .
  7. ^ Werner Krause, Heinz Jürgen Bernhardt, Herta Effenberger, Thomas Witzke: Schneebergite and nickelschneebergite from Schneeberg, Saxony, Germany: the first bi-bearing members of the tsumcorite group . In: European Journal of Mineralogy . tape 14 , 2002, p. 115-126 , doi : 10.1127 / 0935-1221 / 02 / 0014-0115 .
  8. ↑ 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]).
  9. ↑ a b Stefan Weiß: Cobalt solder armeyerite . In: Lapis . tape 25 , no. 2 , 2000, pp. 34 .
  10. ↑ a b c Georges Favreau, Jacques Emile Dietrich: The minerals of Bou Azzer . In: Lapis . tape 31 , no. 7–8 , 2006, pp. 49, 51, 54 .
  11. ↑ Mindat - Number of localities for cobalt solder armeyerite
  12. ↑ a b c d List of locations for cobalt solder armyerite in the Mineralienatlas and Mindat
  13. ↑ Stefan Weiß: From Brendelit to Schlegelit: First descriptions of Schneeberger 1998-2003 . In: Lapis . tape 30 , no. 7–8 , 2005, pp. 67-68 .
  14. ↑ Halil Sarp, Georges Favreau: Seconde occurrence du nouveau mineral cobaltlotharmeyerite Ca (Co, Fe, Ni) 2 [AsO 4 ] 2 (OH, H 2 O) 2 . In: Archives des sciences et compte rendu des séances de la Société / édités par la Société de physique et d'histoire naturelle de Genève . tape 53 , no. 1 , 2000, pp. 49-54 .