Euxenite- (Y)

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Euxenite- (Y)
Euxenite- (Y) -263711.jpg
Euxenite (Y) from the Luella pegmatite, Buena Vista (Colorado) , USA (size: 5.8 cm × 4.8 cm × 3.3 cm)
General and classification
chemical formula (Y, Ca, Ce, U, Th) (Nb, Ta, Ti) 2 O 6
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.DG.05 ( 8th edition : IV / D.19)
03/08/08/02
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Room group (no.) Pbcn (No. 60)
Lattice parameters a  = 14.64  Å ; b  = 5.55 Å; c  = 5.19 Å
Formula units Z  = 4
Twinning generally after {201}, rarely after {101} and {013}
Physical Properties
Mohs hardness 5.5 to 6.5 (VHN 50 = 633 to 692)
Density (g / cm 3 ) measured: 5.3 to 5.9; calculated: [5.16]
Cleavage Please complete!
Break ; Tenacity clamshell; brittle
colour black, brownish black, greenish black
Line color yellowish, greyish or reddish brown
transparency opaque, shining through in thin layers
shine weak metallic sheen, wax to resin sheen on broken surfaces
radioactivity weak
Crystal optics
Refractive index n  = 2.06 to 2.24
Birefringence isotropic because it is metamictic

Euxenite- (Y) is a rather seldom occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the orthorhombic crystal system with the chemical composition (Y, Ca, Ce, U, Th) (Nb, Ta, Ti) 2 O 6 . The elements yttrium , calcium , cerium , uranium and thorium or niobium , tantalum and titanium 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.

Euxenite- (Y) usually develops sturdy, prismatic crystals , but also occurs in the form of radial mineral aggregates . Its color varies between black, brownish black and greenish black and its line color between yellowish, grayish and reddish brown.

Etymology and history

Was first discovered Euxenit- (Y) of Baltazar Mathias Keilhau in an unnamed pegmatite -Formation at Jølster in the Norwegian province Sogn og Fjordane and described in 1840 by Theodore Scheerer (1813-1875), of the mineral after the Greek word Greek εύξενος [euxenos ] named for hospitable because it houses many rare ingredients.

In 1987 the mineral name was adapted by the International Mineralogical Association (IMA) due to its predominant component yttrium after euxenite- (Y).

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the euxenite (Y) belonged to the department of "Oxides with a molar ratio of metal: oxygen = 1: 2 (MO 2 and related compounds)", where he gave the name "Euxenit series" with the system no. IV / D.19 and the other members Calciosamarskit , Fersmit , Ishikawait , Loranskit- (Y) , Písekit- (Y) , Polykras- (Y) , Samarskit- (Y) , Samarskit- (Yb) , Tanteuxenit- (Y) , Uranopolykras , yttrocolumbit- (Y) , yttrokrasit- (Y) and yttrotantalite- (Y) .

The 9th edition of Strunz's mineral systematics, which has been in force since 2001 and is used by the IMA, also classifies the euxenite (Y) in the category of "oxides with the molar ratio of metal: oxygen = 1: 2 and comparable". However, this is further subdivided according to the relative size of the cations involved and the crystal structure , so that the mineral is classified in the sub-section “With large (± medium-sized) cations; Chains of edge-linked octahedra "can be found, where the" Euxenite group "with the system no. 4.DG.05 and the other members Fersmit, Kobeit- (Y), Loranskit- (Y), Polykras- (Y), Tanteuxenit- (Y), Uranopolykras and Yttrokrasit- (Y).

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns euxenite- (Y) to the class of "oxides and hydroxides", but there in the category of "multiple oxides with Nb, Ta and Ti". Here it can be found in the unnamed group 08.03.08 within the subsection “Multiple oxides with Nb, Ta and Ti and the formula A (B 2 O 6 )”.

Crystal structure

Euxenite- (Y) crystallizes orthorhombically in the space group Pbcn (space group no. 60) with the lattice parameters a  = 14.64  Å ; b  = 5.55 Å and c  = 5.19 Å as well as 4 formula units per unit cell .

properties

The mineral can be weakly radioactive due to low levels of cerium , uranium and thorium . Taking into account the natural series of decay or existing decay products, the specific activity is given as 80  Bq / g (for comparison: natural potassium 31.2 Bq / g).

Even if the inherent radioactivity of the mineral is rather weak, it nevertheless destroys its crystal structure over time, so that it predominantly occurs metamict .

Education and Locations

Euxenite from Vegusdal , Norway (size 11 cm)
Brown euxenite- (Y) on microcline with light green epidote and dark green chlorite from the Cactus Jack Pegmatite, Burnet County , Texas, USA (field of view about 5 mm)

Euxenite- (Y) forms magmatic in granitic and alkaline pegmatites , but can also be enriched secondarily in soaps . As accompanying minerals may include Aeschynit- (Y) , albite , Allanit , beryl , Betafit , biotite , columbite , gadolinite , grenade , ilmenite , magnetite , microcline , monazite , muscovite , thorite , uraninite , xenotime and zircon occur.

As a rather rare mineral formation, euxenite- (Y) can in part be abundant at various sites, but overall it is not very common. So far (as of 2013) around 400 sites are known to be known. In addition to its type locality Jølster in Sogn og Fjordane , the mineral occurred in Norway among others at Nesodden in Akershus ; in several places in the municipalities of Arendal , Evje og Hornnes , Iveland and Risør in Aust-Agder; at Hurum in Buskerud ; at Drag and Hundholmen in Nordland ; at Tverrbotntind and Sel in Oppland; in different places in Østfold ; at Tørdal and Kragerø in Telemark ; on Kvaløya in Troms; at some sites in Vest-Agder and at Hedrum in Vestfold . Known for the extraordinary finds of euxenite are, among others, Kragerø in Telemark and Hitterø in Vest-Agder, where euxenite crystals up to 15 centimeters long have been found.

In Germany, Euxenit- (Y) has so far been known mainly from Saxony, including from Biesig , Königshain , Thiemendorf (Waldhufen) and Döbschütz in the Görlitz district, but also from the “Steinerleinbach” quarry near Röhrnbach in Lower Bavaria.

In Austria, the mineral has so far been found at Artolz and Gebharts in Lower Austria, at Hopffeldboden ( Hohe Tauern ) in Salzburg and in Zamser Grund in the Zillertal in Tyrol.

In Switzerland Euxenit- (Y) has so far only on Cavloc Lake in Fornotal (Val Forno) in the canton of Grisons , the Gridone in canton Ticino and in de Crête Thyon in Val d'Hérens in the canton of Valais found.

Other locations include Egypt , Ethiopia , Australia , Brazil , China , Finland , France and French Guiana , Guyana , India , Italy , Japan , Canada , Kazakhstan , Kenya , Laos , Madagascar , Mozambique , Namibia , Niger , Portugal , Russia , Sweden , Slovakia , South Africa , South Korea , Swaziland , the Czech Republic and the United States of America (USA).

See also

literature

  • T. Scheerer: About euxenite, a new mineral species. In: Annals of Physics and Chemistry . Volume 50 (1840), pp. 149–153 ( PDF 282 kB )
  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp. 541 (first edition: 1891).
  • H. Weitzel, H. Schrätze: Crystal structure refinements of euxenite, Y (Nb 0.5 Ti 0.5 ) 2 O 6 , and M-fergusonite, YNbO 4 . In: Journal of Crystallography . Volume 152 (1980), pp. 69-82 ( PDF 694 kB )
  • EH Nickel, JA Mandarino: Procedures involving the IMA Commission on New Minerals and Mineral Names and guidelines on mineral nomenclature. In: American Mineralogist. 72, pp. 1031-1042 (1987)

Web links

Commons : Euxenite- (Y)  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b IMA / CNMNC List of Mineral Names; October 2013 (PDF 1.5 MB)
  2. ^ A b c 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.  219 .
  3. ↑ a b c Euxenite- (Y) , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 70, 9 kB )
  4. ↑ Mindat - Euxenite- (Y)
  5. ↑ Webmineral - Euxenite- (Y)
  6. ↑ Mindat - Number of localities for Euxenite- (Y)
  7. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 107 ( Dörfler Natur ).
  8. ↑ Find location list for Euxenit- (Y) at the Mineralienatlas and at Mindat