Abswurmbachit

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Abswurmbachit
General and classification
other names

IMA 1990-007

chemical formula
  • Cu 2+ Mn 3+ 6 O 8 (SiO 4 )
  • Cu 2+ Mn 3+ 6 3+ [O 8 | SiO 4 ]
  • (Cu 2+ , Mn 2+ ) Mn 3+ 6 [O 8 | SiO 4 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.AG.05
07.05.01.04
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol ditetragonal-dipyramidal; 4 / m  2 / m  2 / m
Space group I 4 1 / acd (No. 142)Template: room group / 142
Lattice parameters a  = 9.41  Å ; c  = 18.55 Å
Formula units Z  = 8
Physical Properties
Mohs hardness 6.5 ( VHN 25  = 870–950, average 920)
Density (g / cm 3 ) calculated: 4.96 (synthetic)
Cleavage is missing
colour black
Line color brownish black
transparency opaque
shine Metallic luster

The Abswurmbachit is a very rare mineral from the mineral class of "silicates and germanates" with the chemical composition Cu 2+ Mn 6 3+ [O 8 | SiO 4 ] and is chemically a copper - manganese - silicate with additional oxygen ions . Structurally, Abswurmbacht belongs to the island silicates .

Worm bachite crystallizes in the tetragonal crystal system and has so far only been found in the form of microcrystalline, black grains of around 50 μm in size.

With Braunite (Mn 2+ Mn 3+ 6 [O 8 | SiO 4 ]), Abswurmbachite forms a gapless mixed crystal row .

Etymology and history

Abswurmbachit was found for the first time near Myli (also Mili ) on Mount Ochi on the island of Evia and near Apikia (also Apoikia ) on Mount Vasilikon on the island of Andros in Greece. The mineral was analyzed and described by Thomas Reinecke, Ekkehart Tillmanns and Heinz-Jürgen Bernhardt, who named it after the German mineralogist Irmgard Abs-Wurmbach (* 1938), daughter of, in recognition of their contributions to crystal chemistry, the stability relationships and the physical properties of Braunite Zoologist Hermann Wurmbach , named. Since material from both Greek sites was used for the analysis, both are also considered to be type localities .

Abswurmbachite was recognized as an independent mineral in 1990 by the International Mineralogical Association (IMA) under the number IMA 1990-007 . The research results and the recognized name were published a year later in the science magazine “New Yearbook for Mineralogy” (Abh .: 163).

Type material of the mineral is kept in the Smithsonian Institution in Washington DC as well as in the Institute for Mineralogy, Geology and Geophysics of the Ruhr University Bochum .

classification

Since the Abswurmbachite was only recognized as an independent mineral in 1990, it is not yet listed in the 8th edition of the mineral classification according to Strunz , which has been outdated since 1977 . Only in the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this classic classification by Karl Hugo Strunz , the mineral received the system and mineral number. VIII / B.09-05 . In the "lapis system" this corresponds to the class of "silicates and germanates" and there to the department " island silicates with non-tetrahedral anions ", where Abswurmbachit together with Braunite , Franciscanite , Gatedalit , Katoptrit , Långbanit , Neltnerit , Örebroit , Welinite , Yeatmanite one forms an independent but unnamed group (as of 2018).

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies Abswurmbachite under the category of "island silicates (nesosilicates)". This is further subdivided according to the possible presence of additional anions and the coordination of the cations involved , so that the mineral is classified according to its composition in the subdivision of “island silicates with additional anions; Cations are mostly found in [6] er and> [6] er coordination ", where the" Braunite group "with the system no. Is only found together with Braunite, Braunite II and Neltnerite. 9.AG.05 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns worm bachite, on the other hand, to the class of "oxides and hydroxides". Here it is together with Braunit-I, Braunit-II and Neltnerite in the "humite group (tetragonal: I 4 1 / acd ) with Si" with the system no. 07.05.01 to be found within the subsection of " Multiple oxides with the formula ABX 2 ". Template: room group / 142

Crystal structure

Abswurmbachite crystallizes tetragonally in the space group I 4 1 / acd (space group no. 142) with the lattice parameters a  = 9.41  Å and c  = 18.55 Å and 8 formula units per unit cell . Template: room group / 142

Modifications and varieties

Between Abswurmbachite and Braunite there is a gapless series of mixed crystals in which copper is gradually being replaced by manganese . Another similar mineral is neltnerite , which contains calcium instead of copper . However, there is probably a miscibility gap between Abswurmbachite and Neltnerite, so that no mixed crystal series is possible.

Education and Locations

Abswurmbachite forms together with Braunite in manganese - and aluminum - containing Piedmontite - Sursassite - quartzites at pressures of 7 to 11 kbar and temperatures of 300 to 420 ° C. Other accompanying minerals include ardennite , hollandite , clinochlorine , quartz , rutile and shattuckite .

The mineral is so rare that so far (2018) it is only known in a few samples from fewer than 10 localities. Its type localities Myli ( Mili ) and Apikia ( Apoikia ) are so far the only known sites in Greece.

The only known site in Germany so far is near Ramsbeck in the Sauerland community of Bestwig in North Rhine-Westphalia. Abswurmbachit is also known from Papachacra in the Argentine Department of Belén , from the Solfatara di Pozzuoli in the Italian region of Campania and from Iyomishima (today: Shikokuchūō ) on the Japanese island of Shikoku .

See also

literature

  • Thomas Reinecke, Heinz-Jürgen Bernhardt, Ekkehart Tillmanns: Abswurmbachite, Cu 2+ Mn 6 3+ [O 8 | SiO 4 ], a new mineral of the braunite group: natural occurrence, synthesis, and crystal structure . In: New Yearbook for Mineralogy, Treatises . tape 163 , 1991, pp. 117–143 (deposited in OTRS ).
  • John Leslie Jambor : New Mineral Names . In: American Mineralogist . tape 77 , 1992, pp. 670–675 ( minsocam.org [PDF; 732 kB ; accessed on October 15, 2019]).

Web links

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: September 2019. (PDF 2672 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, September 2019, accessed October 15, 2019 .
  2. ↑ a b c d e f 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.  553 .
  3. ↑ a b c d e f g 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 .
  4. ↑ David Barthelmy: Abswurmbachite Mineral Data. In: webmineral.com. Retrieved October 15, 2019 .
  5. ↑ a b Abswurmbachite . 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; 67  kB ; accessed on October 15, 2019]).
  6. ^ Hermann Wurmbach: Foreword to the second edition . In: Textbook of Zoology . 2nd, completely revised edition. tape 1 : General zoology and ecology . G. Fischer, Stuttgart 1970, p. VIII .
  7. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed October 15, 2019 .
  8. ↑ a b Thomas Reinecke, Heinz-Jürgen Bernhardt, Ekkehart Tillmanns: Abswurmbachite, Cu 2+ Mn 6 3+ [O 8 | SiO 4 ], a new mineral of the braunite group: natural occurrence, synthesis, and crystal structure . In: New Yearbook for Mineralogy, Treatises . tape 163 , 1991, pp. 117–143 (deposited in OTRS ).
  9. ↑ Find location list for Abswurmbachite in the Mineralienatlas and Mindat , accessed on October 15, 2019.