Althausite

Althausite
	Althausite (dark reddish brown), hematite (dark gray) and lizardite (greenish white serpentine talc matrix) from the Overntjern quarry, Modum, Buskerud, Norway (size 8.0 cm × 4.0 cm × 3.0 cm)
General and classification
other names	IMA 1974-050
chemical formula	Mg 4 (PO 4 ) 2 (OH, O) (F, □); Mg 2 [(OH, F) \| PO 4 ];
Mineral class; (and possibly department)	Phosphates, arsenates and vanadates
System no. to Strunz ; and to Dana	8.BB.25 ( 8th edition : VII / B.04) ; 06/41/05/01
Crystallographic Data
Crystal system	orthorhombic
Crystal class ; symbol	orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Space group	Pnma (No. 62)
Lattice parameters	a = 8.258 (2) Å ; b = 6.054 (2) Å; c = 14.383 (5) Å
Formula units	Z = 4
Frequent crystal faces	{010}, {110}, {131}
Physical Properties
Mohs hardness	3.5 to 4
Density (g / cm 3 )	measured: 2.97 (2); calculated: 2.91
Cleavage	completely after {001}, clearly after {101}
Break ; Tenacity	brittle
colour	light gray, reddish brown
Line color	White
transparency	translucent
shine	Glass gloss
Crystal optics
Refractive indices	n α = 1.588 ; n β = 1.592 ; n γ = 1.598
Birefringence	δ = 0.010
Optical character	biaxial positive
Axis angle	2V = 70 ° (measured); 80 ° (calculated)

Althausite is a very rarely occurring mineral from the mineral class of “phosphates, arsenates and vanadates” with the chemical composition Mg ₄ (PO ₄ ) ₂ (OH, O) (F, □). From a chemical point of view, it is therefore a magnesium - phosphate with additional hydroxide, oxygen - and / or fluorine ions . The compounds or elements OH and O indicated in the round brackets can represent each other in the formula ( substitution , diadochy), but are always in the same proportion to the other components of the mineral. Some of the fluorine can also be absent; H. the corresponding place in the crystal lattice would be a blank space .

Althausite crystallizes in the orthorhombic crystal system and is found in nature mostly in the form of coarse mineral aggregates and fissile masses that can weigh up to a few hundred grams . However, it rarely develops clumsy, tabular and translucent crystals up to about three centimeters in size, which are stretched along the longitudinal axis and have a glass-like sheen on the surface . Depending on foreign admixtures , including inclusions of magnetite or xenotime , its color varies between light gray and reddish brown. His line color , however, is always white.

The mineral is brittle and can be split very easily at right angles to the c-axis (longitudinal axis) . Over time it transforms into apatite along the cleavage planes .

Etymology and history

Althausit quarry Tingelstadtjern near Modum in the Norwegian province of Buskerud was first discovered and described in 1975 by Gunnar Raade and Magne Tysseland , who named the mineral after the German mineralogist Egon Althaus .

Type material of the mineral is kept in the Mineralogical-Geological Museum of the University of Oslo in Norway (Catalog No. 22044, 22045).

classification

Althausite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates, with foreign anions F, Cl, O, OH", in the outdated, but partly still in use, 8th edition of the mineral classification according to Strunz . where together with holtedahlite , phosphoellenbergerite and satterlyite it formed the unnamed group VII / B.04 .

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 althausite to the category of “phosphates etc. with additional anions; without H ₂ O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the other anions (OH etc.) to the phosphate, arsenate or vanadate complex (RO ₄ ), so that the mineral according to its composition in the sub-section “With exclusively medium-sized cations; (OH etc.): RO ₄ ≤ 1: 1 “can be found where it is the only member of the unnamed group 8.BB.25 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns althausite to the class of "phosphates, arsenates and vanadates" and there to the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is to be found as the only member / together with in the unnamed group 41.06.05 within the subdivision "Anhydrous phosphates etc., with hydroxyl or halogen with (A) ₂ (XO ₄ ) Z _q ".

Crystal structure

Althausite crystallizes orthorhombically in the space group Pnma (space group no. 62) with the lattice parameters a = 8.258 (2) Å ; b = 6.054 (2) Å and c = 14.383 (5) Å and 4 formula units per unit cell .

Modifications and varieties

The compound Mg ₂ [(OH, F) | PO ₄ ] is dimorphic and occurs naturally as a trigonal crystallizing holtedahlite in addition to the orthorhombic crystallizing althausite .

Education and Locations

Althausit forms in serpentine - magnesite - deposits . As Begleitminerale occur next apatite, magnetite and xenotime, you still arsenopyrite , chalcopyrite , chlorite , enstatite , Holtedahlit, magnesite, muscovite , Panasqueirait , pyrrhotite , quartz , siderite , sphalerite , Szaibélyit , Thadeuit , talc , topaz , Vivianit and Wolfeit on.

As a very rare mineral formation, althausite has so far only been found in a few samples from a total of three sites (as of 2014). In addition to its type of locality , the Tingelstadtjern quarry, these are also the Overntjern quarry , which is also close to Modum , and the tin-tungsten deposit in the Panasqueira mining area ( Couto Mineiro da Panasqueira ) near the city of Covilhã in Portugal.

literature

Gunnar Raade , Magne Tysseland: Althausite, a new mineral from Modum, Norway. Lithos, Volume 8 (1975), pp. 215-219 doi: 10.1016 / 0024-4937 (75) 90038-9
Michael Fleischer , Louis J. Cabri: New mineral names. In: American Mineralogist. Volume 61 (1976), pp. 502–504 ( PDF 400.5 kB )
C. Rømming, Gunnar Raade: The crystal structure of althausite, Mg ₄ (PO ₄ ) ₂ (OH, O) (F, □). In: American Mineralogist. Volume 65 (1980), pp. 488–498 ( PDF 1.6 MB )

Web links

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

Individual evidence

↑ ^a ^b ^c ^d ^e C. Rømming, Gunnar Raade: The crystal structure of althausite, Mg ₄ (PO ₄ ) ₂ (OH, O) (F, □). In: American Mineralogist. Volume 65 (1980), pp. 488–498 ( PDF 1.6 MB )
^ 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. 443 .
↑ ^a ^b ^c ^d ^e Althausite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.4 kB )
↑ ^a ^b ^c ^d ^e ^f Mindat - Althausite
↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 628 .
^ ^A ^b Michael Fleischer , Louis J. Cabri: New mineral names. In: American Mineralogist. Volume 61 (1976), pp. 502–504 ( PDF 400.5 kB )
↑ Find location list for Althausite at the Mineralienatlas and at Mindat

[RømmingRaade-1] C. Rømming, Gunnar Raade: The crystal structure of althausite, Mg ₄ (PO ₄ ) ₂ (OH, O) (F, □). In: American Mineralogist. Volume 65 (1980), pp. 488–498 ( PDF 1.6 MB )

[StrunzNickel-2] 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. 443 .

[Datenblatt-3] Althausite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.4 kB )

[Mindat-4] ↑ ^a ^b ^c ^d ^e ^f Mindat - Althausite

[Lapis-5] Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .

[Klockmann-6] Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 628 .

[AM-61-1976-7] A ^b Michael Fleischer , Louis J. Cabri: New mineral names. In: American Mineralogist. Volume 61 (1976), pp. 502–504 ( PDF 400.5 kB )

[Fundorte-8] Find location list for Althausite at the Mineralienatlas and at Mindat