Beraunit

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Beraunit
Beraunite-91804.jpg
Beraunite from the Mark mine, Essershausen , Weilburg , Wetzlar district , Hesse
General and classification
chemical formula Fe 2+ Fe 3+ 5 [(OH) 5 | (PO 4 ) 4 ] • 6H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DC.27 ( 8th edition : VII / D.11)
11.11.16.01
Crystallographic Data
Crystal system Monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / c (No. 15)Template: room group / 15
Lattice parameters a  = 20.95  Å ; b  = 5.17 Å; c  = 19.27 Å
β  = 93.3 °
Formula units Z  = 4
Twinning Penetration twins according to {100}
Physical Properties
Mohs hardness 3 to 4
Density (g / cm 3 ) measured: 2.8 to 3.08; calculated: 2.894
Cleavage good after {100}
Break ; Tenacity brittle
colour dull green to green-brown, red-brown, blood-red
Line color cloudy olive green when fresh, yellow-brown when oxidized
transparency Translucent
shine Glass luster, resin luster, pearlescent luster at cracks
Crystal optics
Refractive indices n α  = 1.707 to 1.775
n β  = 1.735 to 1.786
n γ  = 1.738 to 1.820
Birefringence δ = 0.031 to 0.045
Optical character biaxial positive
Axis angle 2V = measured: 30 ° to 60 °; calculated: 66 °
Other properties
Chemical behavior soluble in acids

Beraunite is a rather rare mineral of the mineral class of phosphates, arsenates and vanadates with the chemical composition Fe 2+ Fe 3+ 5 [(OH) 5 | (PO 4 ) 4 ] · 6H 2 O and is therefore chemically a water-containing iron - Phosphate with additional hydroxide ions .

Beraunite crystallizes in the monoclinic crystal system and mostly develops tabular crystals of up to one centimeter in size. He can also form coarse needles in mineral aggregates .

With a Mohs hardness of 3 to 4, beraunite is one of the soft to medium-hard minerals.

Etymology and history

The mineral was first described in 1941 by August Breithaupt in his Complete Manual of Mineralogy . He found it in the Beraun district (today Beroun ) in Bohemia , today's Czech Republic . The mineral was later examined in more detail by Clifford Frondel . He examined the chemical composition and came up with a formula between Fe 3+ 5 [(PO 4 ) 3 | (OH) 6 ] 2 · 1 / 4 H 2 O and Fe 2+ Fe 3+ 4 [(PO 4 ) 3 | (OH) 5 ] · 2 1 / 2 H 2 O. Today formula applies Fe 2+ Fe 3+ 5 [(OH) 5 | (PO 4 ) 4 ] · 6H 2 O, so Beraunit substantially contains more water of crystallization , as was accepted by Frondel.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the beraunite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions ", where together with Strunzit it belonged to the "Strunzit -Beraunit Group "with the system no. VII / D.11 and the other members Bermanit , Burangait , Dufrénit , Ercitit , Ferristrunzit , Ferrostrunzit , Gormanit , Kakoxen , Kidwellit , Laubmannit , Matioliit , Meurigit-K , Meurigit-Na , Natrodufrénit , Oxiberaunit , Souzalite and Tinticit bildete .

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 Beraunit to the category of “phosphates etc. with 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 the additional anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4  = 1: 1 and <2: 1 “can be found, where it forms the unnamed group 8.DC.27 on its own.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Beraunite to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here it can be found alone in an unnamed group with the system number 42.11.16 within the sub-section “Water-containing phosphates etc., with hydroxyl or halogen with (AB) 4 (XO 4 ) 3 Z q  × x (H 2 O)”.

Crystal structure

Beraunite crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a  = 20.943  Å , b  = 5.129 Å, c  = 19.213 and Å, β = 93.67 ° and 4 formula units per unit cell. Template: room group / 15

The iron atoms are six-coordinate in the lattice structure. The phosphate anions ([PO 4 ] 3− ) form tetrahedra .

properties

Beraunit is readily soluble in acids .

Education and Locations

Beraunite occurs in traces in iron ore , as well as in clay and sand . It is a secondary mineral to triphyline . Beraunite forms parageneses with vivianite , dufrénite , rockbridgeite , wavellite , ferristrunzite , frondelite , hureaulite , mitridatite , stewartite , laueit , leukophosphite , triphyline and limonite .

Beraunite occurs at around 150 sites.

The type locality is in the Czech Republic in the Beroun district and there in St. Benigna (Svatá Dobrotivá) in the "Hrbek Mine". Other locations in the Czech Republic are Kutterberg (Kutná Hora). In the Karlovy Vary region there is one site in Krásno nad Teplou (Schönfeld) and two sites in the Pilsen region . There is also a site in the Vysočina region .

In Germany there are about 25 localities. In Baden-Württemberg there is a site in Wolfach in the Black Forest . There are many sites in Bavaria , most of them in the Upper Palatinate (in the communities Auerbach , Pleystein , Plößberg and Waidhaus ), but there is one in Bavaria in the Lower Bavaria region in Rabenstein . In Hesse there are sites in the Wetzlar district in Rodheim-Bieber , in Waldgirmes and in Weilburg . In North Rhine-Westphalia there is a site in the Sauerland in Uentrop (city of Arnsberg ), and in Wuppertal near Aprath Castle . In Saxony there is a site in the Ore Mountains in the Annaberg district , as well as two sites in Görlitz in Upper Lusatia and one site in Auerbach in the Vogtland . In Schleswig-Holstein there is a site in Jodelund . In Thuringia, there is one site in the Harz Mountains and one in the Vogtland.

In Austria there are three sites in Styria . The first in Eisenerz , a second in the Koralpe mountain range in Modriach and a third in Leoben .

In Switzerland there is a site in Brissago in the canton of Ticino .

There are other sites in Australia , Belgium , Brazil , France , Ireland , Italy , Japan , Cameroon , Mali , Morocco , the Netherlands , Portugal , Russia , Spain , Sweden , the Czech Republic , Hungary , in the United Kingdom in England and in the US states Alabama , Arizona , Arkansas , Connecticut , Florida , Georgia , Indiana , Maine , Montana , Nevada , New Hampshire , New Jersey , New Mexico , North Carolina , Pennsylvania , South Carolina , South Dakota, and Tennessee .

See also

literature

  • YMF Cossato, P. Orlandi, M. Pasero: Manganese-bearing beraunite from Mangualde, Portugal: mineral data and structure refinement . In: The Canadian Mineralogist . tape 27 , 1989, pp. 441–446 ( rruff.info [PDF; 683 kB ; accessed on April 23, 2018]).
  • Paul B. Moore, AR Kampf: Beraunite: Refinement, comparative crystal chemistry, and selected bond valences . In: Journal of Crystallography . tape 201 , 1992, pp. 263–263 ( rruff.info [PDF; 417 kB ; accessed on April 23, 2018]).

Web links

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

Individual evidence

  1. ↑ 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.  499 .
  2. ↑ a b c d e f g Beraunite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 66  kB ; accessed on April 23, 2018]).
  3. ↑ a b c d Mindat - Beraunite (English)
  4. ↑ a b c Mineralienatlas: Beraunit
  5. ↑ August Breithaupt: Beraunit . In: Complete Handbook of Mineralogy . 1941 ( rruff.info [PDF; 101 kB ; accessed on April 23, 2018]).
  6. ↑ Clifford Frondel: The dufrenite trouble . In: American Mineralogist . tape 34 . Mineralogical Society of America, 1949, pp. 537 ( rruff.info [PDF; 1.9 MB ; accessed on April 23, 2018]).
  7. ↑ a b c d e f List of localities for Beraunite in the Mineralienatlas and Mindat