Schneiderhöhnit

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Schneiderhöhnit
Schneiderhohnite-37832.jpg
Schneiderhöhnite crystal from the Tsumeb Mine near Tsumeb, Oshikoto Region , Namibia , (step size: 1.5 cm × 1.2 cm × 0.6 cm)
General and classification
other names

IMA 1973-046

chemical formula
  • Fe 2+ Fe 3+ 3 As 3+ 5 O 13
  • 8FeO · 5As 2 O 3 or Fe 8 As 10 O 23
  • 2FeO · 3Fe 2 O 3  · 5As 2 O 3 or Fe 8 As 10 O 26
Mineral class
(and possibly department) 		Oxides and hydroxides (including V [5,6] vanadates, arsenites, sulfites, selenites, tellurites and iodates)
System no. to Strunz
and to Dana 		4.JA.35 ( 8th edition : IV / J.06)
45.01.12.01
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Space group P 1 (No. 2)Template: room group / 2
Lattice parameters a  = 8.945  Å ; b  = 10.022 Å; c  = 9.161 Å,
α  = 62.942 °; β  = 116.072 °; γ  = 81.722 °
Formula units Z  = 2
Physical Properties
Mohs hardness ≈ 3
Density (g / cm 3 ) 4.30 (measured); 4.33 to 4.40 (calculated)
Cleavage completely according to (100), clearly in two further directions
Break ; Tenacity mica-like; brittle
colour dark brown, almost black, yellow-brown to yellow-orange; yellowish-brown to dark brown in transmitted light, red-brown in reflected light with brownish-red internal reflections
Line color coffee brown
transparency opaque, translucent edges
shine Metal luster to diamond luster, semi-metallic luster, resin luster to semi-diamond luster
Crystal optics
Refractive indices n α  > 2.11
n γ  = <2.13
Birefringence δ = 0.020
Optical character biaxial positive
Pleochroism very distinct from red-brown to light yellow

Schneiderhöhnite is a rarely occurring mineral from the mineral class of " oxides and hydroxides (and relatives, see classification)". It crystallizes in the triclinic crystal system with the idealized composition Fe 2+ Fe 3+ 3 As 3+ 5 O 13 , so from a chemical point of view it is an iron - arsenite with divalent and trivalent iron.

Schneiderhöhnite is a typical secondary mineral and arises in arsenic-containing non-ferrous metal deposits through the oxidation of arsenic and iron-containing primary minerals. It is found at its type locality in the form of idiomorphic, often spindle-shaped crystals up to 3 cm in size, which are typically flattened and curved. The mineral also occurs in aggregates .

The type locality of the mineral is the so-called second or "deep" oxidation zone (mining West 120, a few meters below the 29th level) of the Tsumeb Mine near Tsumeb , Oshikoto region , Namibia .

Etymology and history

Schneiderhöhnite was first found in 1972 by the Tsumeber mine geologist TL Krüger when opening a gap. Krüger made this mineral available to the authors of the type publication for identification. Corresponding investigations led to the determination of the presence of a new mineral which was recognized in 1973 by the International Mineralogical Association (IMA) under the provisional designation IMA 1973-046. A German research team with Joachim Ottemann , Bernhard Nuber and Bruno H. Geier carried out the first scientific description of this mineral as Schneiderhöhnite ( English Schneiderhöhnite ) in 1973 in the German science magazine "New Yearbook for Mineralogy, MONTHS" . The authors named the mineral after the German mineralogist, geologist, depository scientist and university professor Hans Schneiderhöhn (1887–1962) from the Albert Ludwig University in Freiburg im Breisgau in recognition of his fundamental work on understanding the geology and mineralogy of the Tsumeber deposit and similar deposits in the Otavi mountainous region.

The type material for Schneiderhöhnit is listed under catalog no. M33238 in the Royal Ontario Museum in Toronto , Ontario , Canada , and at Harvard University in Cambridge , Massachusetts , USA , (catalog no. 111932).

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Schneiderhöhnite belonged to the department of "Arsenite (with As 3+ )", where together with Fetiasite , Gebhardit , Paulmooreit and Vajdakit it formed the group of "Arsenite with [As 2 O 5 ] 4− groups ”with the system no. IV / J.06 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 Schneiderhöhnite in the newly defined division of “arsenites, antimonites, bismuthites, sulfites, selenites and tellurites”. This is further subdivided according to the possible presence of crystal water and / or additional anions , so that the mineral is classified in the sub-section “Arsenites, Antimonides, Bismutites; without additional anions, without H 2 O “, where it is the only member of the unnamed group 4.JA.35 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Schneiderhöhnite to the class of "phosphates, arsenates and vanadates" and there to the category of "acids and normal antimonites, arsenites and phosphites". Here he is the only member of the unnamed group 45.01.12 within the sub-section “ Acid and normal antimonites, arsenites and phosphites with various formulas ”.

Chemism

Three microprobe analyzes on Schneiderhöhnite from the Tsumeb mine resulted in mean values ​​of 27.90% Fe; 0.93% Zn; 0.37% Ge; 29.20% (Fe + Zn + Ge); 47.03 As and 29.29% O (determined by difference to 100%). From this, the empirical formula 8 (Fe 0.96 Zn 0.03 Ge 0.01 ) O · 5As 2 O 3 was calculated, which was simplified to 8FeO · 5As 2 O 3 or Fe 8 As 10 O 23 . The presence of both divalent and trivalent iron had not yet been recognized in the type publication. This was only discovered during the investigations by Bernhard Nuber, who gave the chemical formula as 2FeO · 3Fe 2 O 3  · 5As 2 O 3 or Fe 8 As 10 O 26 . The formula was first used by Frank Hawthorne in the form commonly used today with Fe 2+ Fe 3+ 3 As 3+ 5 O 13 . This ideal formula requires a content of 27.72% Fe; 46.48 As and 25.80% O (total 100.00% by weight).

Only angelellite , Fe 3+ 4 (AsO 4 ) 2 O 3 , and caribibite , Fe 3+ 3 (As 3+ O 2 ) 4 (As 3+ 2 O 5 ) (OH), are chemically similar , with both minerals only being trivalent Contain iron.

Crystal structure

Schneiderhöhnite crystallizes triclinically in the space group P 1 (space group no. 2) with the lattice parameters a  = 8.945  Å ; b  = 10.022 Å; c  = 9.161 Å; α = 62.942 °; β = 116.072 ° and γ = 81.722 ° as well as two formula units per unit cell . Template: room group / 2

The structure of the Schneiderhöhnite was described in 1985, following a suggestion by Frank Hawthorne, as a framework structure. However, detailed investigations have shown that the structure of the Schneiderhöhnite can be better understood as a layered structure than as a framework structure. In the crystal structure of Schneiderhöhnite there are zigzag chains of Fe (1), Fe (2), Fe (3) octahedra (= Fe 3+ ) with common edges parallel to the c-axis [001]. These chains are cross-linked by tetramers of Fe (4) octahedra (= Fe 3+ ) and Fe (5) octahedra (= Fe 2+ ), which also have common edges, to form a corrugated layer. Trigonal (As 3+ O 3 ) pyramids decorate the surface of this layer as individual (AsO 3 ) groups, with all three short bonds connected with anion vertices of the octahedra. The same applies to the two crystallographically different [As 2 O 5 ] dimers with four short bonds (two of each As 3+ ) to the corner points of the octahedron. The layers are linked in the [100] direction by the bridging anion of one of the two [As 2 O 5 ] dimers, which is connected to an Fe 2+ octahedron of the adjacent layer. In this way the strong layer-like character of the structure and the very perfect cleavage according to (100) are caused.

properties

Schneiderhöhnite crystals from the "Tsumeb Mine" (step size: 2.3 cm × 1.1 cm × 1.0 cm)

morphology

Schneiderhöhnite was found at its type locality in the material of the original find from 1972 in the form of a few crystal aggregates, the largest of which have an edge length of 7 mm. In 1986 groups of perfectly formed crystals up to 12 mm in size were found. The idiomorphic, often spindle-shaped crystals are typically flattened and curved. The largest known Schneiderhöhnite crystal from the "Tsumeb Mine" has a size of 3 cm and must have been found in 1976 or before. Only the surface forms {100}, {010} and {001} appear on the crystals. Schneiderhöhnite from Bou Azzer / Morocco forms prismatic to tabular crystals. Schneiderhöhnite crystals from Oumlil-Ost / Morocco were found in millimeter-sized pointed crystals or beudantite-like pseudorhombohedra with triangular end faces. Khder / Morocco supplied spherical Schneiderhöhnite aggregates up to 5 mm in diameter.

physical and chemical properties

Schneiderhöhnite crystals are dark brown, almost black, or yellow-brown to orange-brown. The streak color of the mineral, on the other hand, is always coffee brown. The surfaces of the opaque and only edge-translucent Schneiderhöhnite show a metallic to diamond-like sheen , which agrees very well with the values ​​for light refraction. Schneiderhöhnite has a very high light refraction (n α  > 2.11; n γ  <2.13) and an average birefringence (δ = 0.020). Under the microscope , Schneiderhöhnite is yellowish brown to dark brown in transmitted light and shows a very clear pleochroism from red brown to light yellow.

In incident (reflected) light, Schneiderhöhnite is red-brown, has only a low reflectivity (much lower than chalcosine) and neither in air nor in oil exhibits bireflectance . With crossed polars, the mineral shows barely noticeable to weak anisotropy effects with greenish to brownish rotational colors. The inner reflections are, especially in immersion oil , clearly reddish brown to brownish red.

Schneiderhöhnite has complete cleavage according to (100) and clear cleavage in two other directions. Due to its brittleness , however , it breaks like chalcophyllite , with the break surfaces being mica-like or leafy. With a Mohs hardness of ≈ 3, the mineral is one of the medium-hard minerals and, like the reference mineral calcite, can be scratched with a copper coin.

The measured density for Schneiderhöhnit is 4.30 g / cm³, the calculated density varies between 4.33 and 4.30 g / cm³ depending on the processor. Schneiderhöhnit is neither in the long term nor in the short wavelength UV light , a fluorescent .

Education and Locations

Schneiderhöhnite forms in the oxidation zone of ore deposits , the arsenic originating from the weathering of the arsenic pale ore tennantite or from lollingite and the iron from the conversion of primary iron sulfides such as pyrite or iron arsenides such as lollingite. In the Tsumeb mine - similar to stottite - the formation temperature is likely to have been around 40 ° C, whereby the mineral paragenesis indicates the effect of a medium oxidation potential, which is also expressed in the composition of the Schneiderhöhnite.

Typical accompanying minerals in the "Tsumeb Mine" are zinc-bearing stottite , Leiteit , chalcosine , tennantite, pyrite and galena . In the Moroccan deposits ("Bou Azzer", "Oumlil-East", "Méchui", "Tamdrost-West" and "Khder"), lollingite, caribibite, eosphorite , arseniosiderite , skorodite , symplesite , pharmacosiderite and Quartz observed. For Oumlil-Ost the succession (formation sequence) quartz → Schneiderhöhnit → Karibibit → Symplesite is given. In the pegmatite "Córrego do Urucum", Schneiderhöhnite occurs in prismatic crystals that have grown together to form parallel aggregates and sits on lollingite together with arseniosiderite, arsenolite , scorodite and caribibite.

Schneiderhöhnite has so far (as of 2018) been described as a very rare mineral formation from around 15 sites. The type locality for Schneiderhöhnite is the second or "deep" oxidation zone (mining West 120, a few meters below the 29th level) of the Tsumeb Mine near Tsumeb , Oshikoto region , Namibia . In Namibia also from the pegmatite “Ariakas No. 2 ”on the Davib East 61 farm near Karibib , Erongo region . In Africa also from various sites in the mining area of ​​Bou Azzer near Taznakht (Tazenakht) such as "Oumlil-East", "Méchui", "Tamdrost-West" and "Khder".

From the “Boca Rica Claim” near Sapucaia do Norte and the “Urucum Claim” (pegmatite “Córrego do Urucum”), both near Galiléia, Minas Gerais , Brazil . From the “Mina Jote” and the “Mina Veta Negra”, both in the Pampa Larga district, Tierra Amarilla , Copiapó province , Atacama region , Chile . From the "White Elephant Mine" on Cicero Peak near Pringle in the Custer District, Custer Co. , South Dakota , United States . In Europe from the "Mina Alcantarilla" near Belalcázar not far from Córdoba , Andalusia , Spain . From the Qalbagebirge (Kalba mountain ridge) as the most south-westerly foothills of the Altai in eastern Kazakhstan , the prospect "Nezam Abad" near Ashour Abad, Lorestan province , Iran , and the tin mine Kiura (Shin-Kiura) near Saiki , Ōita prefecture , Kyushu , Japan .

Sites for Schneiderhöhnite from Germany , Austria and Switzerland are therefore unknown.

use

Due to its rarity, Schneiderhöhnite is a sought-after mineral by mineral collectors, but otherwise of no practical importance.

See also

literature

  • Joachim Ottemann, Bernhard Nuber, Bruno H. Geier: Schneiderhöhnit, a natural iron-arsenic oxide from the deep oxidation zone of Tsumeb . In: New yearbook for mineralogy, monthly books . tape 1973 , no. 11 , 1973, p. 517-523 .
  • Schneiderhöhnite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( rruff.info [PDF; 69 kB ; accessed on July 20, 2018]).
  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 638 .
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 837 (first edition: 1891).

Web links

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

Individual evidence

  1. ↑ a b c d e f g Mark A. Cooper, Frank C. Hawthorne: Refinement of the structure of schneiderhöhnite . In: The Canadian Mineralogist . tape 54 , 2016, p. 707-713 , doi : 10.3749 / canmin.1500102 .
  2. ^ A b 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.  264 .
  3. ↑ Official list of the IMA of all minerals
  4. ↑ 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 Joachim Ottemann, Bernhard Nuber, Bruno H. Geier: Schneiderhöhnit, a natural iron-arsenic oxide from the deep oxidation zone of Tsumeb . In: New yearbook for mineralogy, monthly books . tape 1973 , no. 11 , 1973, p. 517-523 .
  5. ↑ a b Bernhard Nuber: The new mineral Schneiderhöhnit, an iron-arsenic oxide from Tsumeb, its ore paragenesis and crystal structure (dissertation) . Ruprecht-Karls-Universität, Faculty of Natural Sciences, Heidelberg 1975, p. 1-80 .
  6. ↑ a b c d e f g h i Mindat - Schneiderhöhnit (English)
  7. ↑ a b c d e f g h i Schneiderhöhnite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( rruff.info [PDF; 69  kB ; accessed on July 20, 2018]).
  8. ↑ a b c d e Karl Schmetzer, Gerd Tremmel, Wolfgang Bartelke: A paragenesis of rare minerals from Bou-Azzer, Morocco: Parasymplesite, Symplesite, Schneiderhöhnit, Karibibit . In: New Yearbook for Mineralogy, Treatises . tape 138 , 1980, pp. 94-108 .
  9. ↑ a b Georg Gebhard: Tsumeb II. A Unique Mineral Locality . 1st edition. GG Publishing, Grossenseifen 1991, ISBN 978-3-925322-03-7 , pp. 270 .
  10. ^ A b Frank C. Hawthorne: Schneiderhöhnite, Fe 2+ Fe 3+ 3As 3+ 5 O 13 , a densely packed arsenite structure . In: The Canadian Mineralogist . tape 23 , 1985, pp. 675–679 ( rruff.info [PDF; 450 kB ; accessed on July 20, 2018]).
  11. ↑ Paul Keller: Tsumeb / Namibia - one of the most spectacular mineral discovery sites on earth . In: Lapis . tape 9 , no. 7-8 , 1984, pp. 51-52 .
  12. ↑ a b c d Georges Favreau, Jacques Emile Dietrich: The minerals of Bou Azzer . In: Lapis . tape 31 , no. 7–8 , 2006, pp. 45-46 .
  13. ↑ Hugo Strunz, Gerhard Söhnge, Bruno H. Geier: Stottite, a new germanium mineral, and its paragenesis in Tsumeb . In: New yearbook for mineralogy, monthly books . tape 1957 , 1957, pp. 85-96 .
  14. ↑ Schneiderhöhnit from Urucum mine, Galileia, Minas Gerais, Brazil (English)
  15. ↑ Mindat - Number of localities for Schneiderhöhnite (English)
  16. ↑ a b List of localities for Schneiderhöhnite in the Mineralienatlas and Mindat
  17. ↑ Christian Rewitzer, Rupert Hochleitner, Thomas Fehr, Martin Carlos Utrera: Karibibite, schneiderhöhnite, tooeleite and other uncommon secondary minerals in the Nuestra Señora de las Alcantarillas mine, Belalcázar, Córdoba, Spain . In: MineralUp (Revista de Minerales) . tape 2016 , no. 1 , 2016, p. 9-39 .
  18. ↑ Anatoly Vasil'evich Voloshin, Yakov A. Pakhomovsky, Alexander Yu. Bakhchisaraitsev: On karibibite and schneiderhohnite from pegmatites of Eastern Kazakhstan . In: Novye dannye o mineralakh SSSR . tape 36 , 1989, pp. 112-135 (Russian).