Magnussonite

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Magnussonite
Magnussonite, Allactite, Hausmannite, Dolomite-762320.jpg
Hausmannite - dolomite ore with magnussonite (green) and allactite (dark pink) from the type locality Långban , Sweden ( total size : 7.0 cm × 6.5 cm × 2.0 cm)
General and classification
chemical formula
  • Mn 2+ 10 As 3+ 6 O 18 (OH, Cl) 2
  • Mn 2+ 10 [(OH, Cl) 2 | (As 3+ O 3 ) 6 ]
  • Mn 2+ 18 [As 3+ 6 Mn 1+ O 18 ] 2 Cl 2
  • (Mn, Mg, Cu) 5 (AsO 3 ) 3 (OH, Cl).
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.JB.15 ( 8th edition : IV / J.04)
46.01.18.01
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Ia 3 d (No. 230)Template: room group / 230
Lattice parameters a  = 19.68  Å
Physical Properties
Mohs hardness 3.5 to 4
Density (g / cm 3 ) measured: 4.14 to 4.49; calculated: 4.55 to 4.62
Cleavage is missing
Break ; Tenacity clamshell; brittle
colour grass green to emerald green, blue green to light olive green, brownish orange to deep red
Line color white to pale green
transparency transparent to translucent
shine Glass gloss, resin gloss
Crystal optics
Refractive index n  = 1.980 (5) to 1.983
Birefringence none, because optically isotropic, with anomalous birefringence 0.001
Optical character abnormal uniaxial negative

Magnussonite is a very rare mineral from the mineral class of "oxides and hydroxides" with the chemical composition Mn 2+ 10 [(OH, Cl) 2 | (As 3+ O 3 ) 6 ] and therefore chemically related to the oxides manganese - arsenite with additional chlorine - or hydroxide .

Magnussonite crystallizes in the cubic crystal system , but develops only microscopic crystals and is therefore mostly found in the form of fine-grain, crusty coatings and crack fillings as well as grainy to coarse aggregates . The mineral is transparent to translucent and shows a glass-like sheen on the surfaces of the grass-green, emerald-green, blue-green, light olive-green or brownish-orange to deep red crystals . In aggregate form, on the other hand, the gloss is more matt and appears more like resin . Magnussonite leaves a white to pale green line on the marking board .

Etymology and history

Namesake Nils Harald Magnusson (1944)

Magnussonite was first discovered in the Långban manganese-iron deposit (Filipstad municipality) in the Swedish province of Värmland County . It was first described in 1956 by Olof Erik Gabrielson , who named the mineral after the Swedish geologist and former director of the Geological Survey of Sweden, Nils Harald Magnusson . The analysis of the mineral was carried out by R. Blix, who determined the composition with (Mn, Mg, Cu) 5 (AsO 3 ) 3 (OH, Cl).

According to more recent analyzes by Pete J. Dunn and Robert A. Ramik on samples from the type locality Långban, the chemical formula was redefined in 1984 to Mn 10 As 3+ 6 O 18 (OH, Cl) 2 , which in the crystal chemical structural formula notation of Mn 2+ 10 [(OH, Cl) 2 | (As 3+ O 3 ) 6 ].

Type material of the mineral is in the Naturhistoriska riksmuseet (German Natural History Museum ) in Stockholm (Sweden) under the catalog no. g32215 , in the Natural History Museum in London (England) and catalog no. 1963, 233 and at Harvard University in Cambridge (Massachusetts, USA) under catalog no. 106140 and 106337 kept.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the magnussonite belonged to the mineral class of "oxides and hydroxides" (including arsenites, sulfites, selenites, tellurites and iodates) and there to the department of "arsenites (with As 3 + ) “, Where he formed the unnamed group IV / J.04 together with Armangit , Cafarsit , Ekatit , Tooeleit and Zimbabweit .

The 9th edition of Strunz's mineral systematics , valid since 2001 and used by the International Mineralogical Association (IMA), also assigns magnussonite to the class of "oxides" and there to the category of "arsenites, antimonites, bismuthites, sulfites, selenites, Tellurite; Iodate ”. However, this is further subdivided according to the possible presence of additional anions and water of crystallization in the formula, so that the mineral is classified in the sub-section “Arsenite, Antimonite, Bismutite; with additional anions, without H 2 O “is to be found, where it forms the unnamed group 4.JB.15 as the only member .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns magnussonite to the class of "phosphates, arsenates, and vanadates" and there to the category of "basic or halogenated antimonites, arsenites and phosphites". Here he is to be found as the only member in the unnamed group 46.01.03 within the subsection “ Basic or halogen-containing antimonites, arsenites and phosphites with (AB) m (XO 3 ) p Z q ”.

Chemism

The newly defined, idealized chemical composition Mn 10 As 3+ 6 O 18 (OH, Cl) 2 with a ratio of (OH): Cl = 0.75: 0.25 consists of around 41.30% manganese (Mn), 33.80% arsenic (As), 23.46% oxygen (O), 0.11% hydrogen (H) and 1.33 chlorine (Cl).

The first analysis of the mineral samples from Långban, however, showed small admixtures of magnesium and copper and the new analysis by Dunn and Ramik also revealed admixtures of iron and calcium . The empirical composition is calculated on the basis of 6 arsenic atoms as (Mn 9.18 Cu 0.38 Fe 0.22 Ca 0.16 Mg 0.07 ) Σ = 10.01 As 3+ 6.00 O 17.79 ((OH) 2.19 Cl 0.26 ) Σ = 2.45 with the corresponding idealized composition Mn 10 As 3+ 6 O 18 (OH, Cl) 2 .

Crystal structure

Magnussonite crystallizes cubically in the space group Ia 3 d (space group no. 230) with the lattice parameter a  = 19.68  Å and 8 formula units per unit cell . Template: room group / 230

The crystal structure of magnussonite consists of edge and corner-linked MnO 8 cubes, trigonal MnO 6 prisms, MnO 6 octahedra and AsO 3 triangles, which together form a framework with large cavities. These cavities accommodate Mn 1+ and Cl, Mn 1+ being surrounded by six As atoms each.

Education and Locations

At its type locality in Långban , Sweden , magnussonite formed in a metamorphosed iron-manganese ore body, where it occurs in paragenesis with calcite , dixenite , dolomite , hematite , hausmannite , trigonite and serpentines containing manganese .

Magnussonite is one of the very rare mineral formations that were only known in a few samples. Besides Långban the mineral was in Sweden in the also for community Filipstad belonging manganese mine Brattfors at Nordmark where as another Begleitminerale Katoptrit , magnetite , manganosite and Sonolit add occurred and in the ore mine Garpenberg Norra at Garpenberg in the province County Dalarna belonging municipality Hedemora being found.

The only other known site to date is the Sterling Mine near Sterling Hill near Ogdensburg in Sussex County in the US state of New Jersey. Here Magnussonit appeared together with Franklinit , Kraisslit , Willemit and Zinkit .

See also

literature

  • O. Gabrielson: Magnussonite, a new arsenite mineral from the Långban mine in Sweden . In: Arkiv för Mineralogi och Geologi . tape 2 , 1956, p. 133-135 (English).
  • Michael Fleischer : New mineral names . In: American Mineralogist . tape 42 , 1957, pp. 580–586 (English, rruff.info [PDF; 628 kB ; accessed on November 10, 2018]).
  • Paul B. Moore, Takaharu Araki: Magnussonite, manganese arsenite, a fluorite derivative structure . In: American Mineralogist . tape 64 , 1979, pp. 390–401 (English, rruff.info [PDF; 1.3 MB ; accessed on November 10, 2018]).
  • Pete J. Dunn, Robert A. Ramik: Magnussonite, new chemical data, an occurrence at Sterling Hill, New Jersey, and new data on a related phase from the Brattfors mine, Sweden . In: American Mineralogist . tape 69 , 1984, pp. 800–802 (English, rruff.info [PDF; 319 kB ; accessed on November 11, 2018]).

Web links

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

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 1, 2020 .
  2. ↑ a b c d e Stefan Weiss: The great Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  3. ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  266 (English).
  4. ^ A b Michael Fleischer : New mineral names . In: American Mineralogist . tape  42 , 1957, pp. 580–586 (English, rruff.info [PDF; 628 kB ; accessed on November 10, 2018]).
  5. ↑ a b c d e f g h Magnussonite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 71  kB ; accessed on May 1, 2020]).
  6. ↑ a b Magnussonite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 1, 2020 .
  7. ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 981 .
  8. ↑ a b Pete J. Dunn, Robert A. Ramik: Magnussonite, new chemical data, an occurrence at Sterling Hill, New Jersey, and new data on a related phase from the Brattfors mine, Sweden . In: American Mineralogist . tape 69 , 1984, pp. 800–802 (English, rruff.info [PDF; 319 kB ; accessed on November 11, 2018]).
  9. ↑ Ellen Kooijman: Magnussonite type material. In: nrm.se. Naturhistoriska riksmuseet , accessed on May 1, 2020 .
  10. ↑ a b List of localities for magnussonite from the Mineralienatlas and Mindat , accessed on May 1, 2020.