Barberit

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Barberit
Barberiite - Vulcano, Lipari Islands, Italy.jpg
Colorless barberiite crystals from Vulcano , Aeolian Islands, Italy
(image width 1 mm)
General and classification
other names

IMA 1993-008

chemical formula NH 4 [BF 4 ]
Mineral class
(and possibly department) 		Halides
System no. to Strunz
and to Dana 		3.CA.10 ( 8th edition : III / B.01)
02/11/04/01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pnma (No. 62)Template: room group / 62
Lattice parameters a  = 9.08  Å ; b  = 5.68 Å; c  = 7.28 Å
Formula units Z  = 4
Physical Properties
Mohs hardness not defined ( VHN 25 approx. 14.2 kg / mm 2 )
Density (g / cm 3 ) measured: 1.89 (3); calculated: 1.90
Cleavage Please complete!
colour colorless, white
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive index n  = 1.3081
Birefringence δ = 0.000
Optical character biaxial
Axis angle 2V = 90 °
Other properties
Special features very soluble in water

Barberiite is a very rarely occurring mineral from the mineral class of " halides ". It crystallizes in the orthorhombic crystal system with the chemical composition NH 4 [BF 4 ] and is therefore chemically ammonium tetrafluoroborate .

Barberiit usually develops colorless or white, spherical mineral aggregates up to about 2 mm in size, but very rarely also very small, pseudo-hexagonal and wafer-thin crystal tablets about 1 μm thick and about 50 to 300 μm long.

Etymology and history

Barberiit was first discovered in October 1992 at the hottest fumaroles (around 700 ° C) north of the "La Fossa" crater on the Sicilian island of Vulcano and described by Anna Garavelli and Vilippo Vurro, who named the mineral after the Italian volcanologist Franco Barberi (* 1938) named. In the same year the mineral was registered by the International Mineralogical Association (IMA) under the internal accession no. IMA 1993-008 recognized as independent.

Type material of the mineral is kept in the Mineralogical Museum of the University of Bari in Italy.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the barberite belonged to the mineral class of the "halides" and there to the department of the "anhydrous double halides", where together with avogadrite , ferruccite and Knasibfit it formed the "ferruccite ​​group" with the system no. III / B.01 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns the barberite to the class of “halides”, although there it belongs to the “complex halides” section. This is further subdivided according to the crystal structure, so that the mineral can be found in the “Borofluoride” subdivision according to its structure, where it is only together with Avogadrit the “Avogadrit group” with the system no. 3.CA.10 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the barberite to the class of "halides" and there in the department of "complex halides - aluminum fluorides". Here he is the only member of the unnamed group 02/11/04 within the subdivision of “ Complex halides (and aluminum fluorides) with the general composition (A) m B (X) 4 ”.

Crystal structure

Barberiit crystallizes orthorhombically in the space group Pnma (space group no. 62) with the lattice parameters a  = 9.08  Å ; b  = 5.68 Å and c  = 7.28 Å as well as 4 formula units per unit cell . Template: room group / 62

properties

Barberit is very soluble in water and decomposes even in slightly moist air.

Education and Locations

Like the related minerals avogadrite and ferruccite, barberite crystallizes directly ( sublimation ) from the volcanic gases of the active fumaroles . Begleitminerale include solid sulfur , Malladrit , realgar , ammonium chloride , Cannizzarit , Galenobismutit and Bismuthinit .

So far (as of 2014) Barberiit was only able to use its type locality "La Fossa Krater" in Italy in the Anna mine near Alsdorf (North Rhine-Westphalia) in Germany and at Jagnob (Yagnob) near Ravat in the Gissar Valley ( Hissor ) in Tajikistan .

See also

literature

  • Anna Garavelli, Vilippo Vurro: Barberiite, NH 4 BF 4 , a new mineral from Vulcano, Aeolian Islands, Italy . In: American Mineralogist . tape 79 , 1994, pp. 381–384 ( minsocam.org [PDF; 469 kB ; accessed on June 15, 2018]).
  • Barberiite . 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; 70 kB ; accessed on June 15, 2018]).

Web links

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

Individual evidence

  1. ↑ a b c d e 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.  160 (English).
  2. ↑ Webmineral - Barberiite (English)
  3. ↑ a b c Barberiite . 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; 70  kB ; accessed on June 15, 2018]).
  4. ↑ a b c Mindat - Barberiite (English)
  5. ↑ Marco E. Ciriotti, Lorenza Fascio, Marco Pasero: Italian Type Minerals . 1st edition. Edizioni Plus - Università di Pisa, Pisa 2009, ISBN 978-88-8492-592-3 , p. 43 (English).
  6. ↑ Find location list for Barberiit at the Mineralienatlas and at Mindat