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Euxenite-(Y)

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Formula:
(Y,Ca,Ce,U,Th)(Nb,Ti,Ta)2O6
Usually the sum (Nb+Ta) is close to Ti, in other words (Nb+Ta)/Ti ~ 1.
System:
Orthorhombic
Colour:
Black, greenish or ...
Hardness:
5½ - 6½
Name:
From the Greek εΰζευος, friendly to strangers, hospitale, in allusion to the many rare elements that it contains.
Dimorph of:
Isostructural with:
Minerals of the Euxenite (Y)-Polycrase-(Y) series are the most widespread niobates after columbite-(Fe) and pyrochlore.

Compare Nioboaeschynite-(Y).

Classification of Euxenite-(Y)

Approved
4.DG.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
G : With large (+- medium-sized) cations; chains of edge-sharing octahedra
8.3.8.2

8 : MULTIPLE OXIDES CONTAINING NIOBIUM,TANTALUM OR TITANIUM
3 : AB2O6
18.4.5

18 : Niobates and Tantalates
4 : Niobates and tantalates containing both U and rare earths
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Type Occurrence of Euxenite-(Y)

Occurrences of Euxenite-(Y)

Geological Setting:
Granitic pegmatites. Placer deposits.

Physical Properties of Euxenite-(Y)

Vitreous, Greasy, Sub-Metallic
Colour:
Black, greenish or brownish tint at times
Comment:
Brown to yellow brown in transmitted light.
Streak:
Yellowish, grayish, reddish brown
Hardness (Mohs):
5½ - 6½
Hardness (Vickers):
VHN50=633 - 692 kg/mm2
Tenacity:
Brittle
Fracture:
Conchoidal, Sub-Conchoidal
Density:
5.3 - 5.9 g/cm3 (Measured)    5.16 g/cm3 (Calculated)

Crystallography of Euxenite-(Y)

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:
a = 5.5528(6) Å, b = 14.6432(20) Å, c = 5.1953(7) Å
Ratio:
a:b:c = 0.379 : 1 : 0.355
Unit Cell Volume:
V 422.43 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Stout prismatic [001]. The faces are striated parallel to their intersection with {010} Often in parallel or subparallel and slightly radial aggregates of crystals. Massive.
Twinning:
1. On {201}, common. The twins are flattened {010} and striated [001] 2. Possibly on {101}, rare. 3. Possibly on {013}.

Crystallographic forms of Euxenite-(Y)

Crystal Atlas:
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Euxenite-(Y) no.4 - Goldschmidt (1913-1926)
Euxenite-(Y) no.5 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Optical Data of Euxenite-(Y)

Type:
Isotropic
RI values:
n = 2.06 - 2.24
Max Birefringence:
δ = 0.000 - Isotropic minerals have no birefringence
Surface Relief:
Very High
Type:
Isotropic

Chemical Properties of Euxenite-(Y)

Formula:
(Y,Ca,Ce,U,Th)(Nb,Ti,Ta)2O6

Usually the sum (Nb+Ta) is close to Ti, in other words (Nb+Ta)/Ti ~ 1.
Idealised Formula:
YNbTiO6
Essential elements:
All elements listed in formula:

Relationship of Euxenite-(Y) to other Species

Series:
Forms a series with Polycrase-(Y) (see here)
4.DG.05Fersmite(Ca,Y)(Nb,Ta,Ti)2(O,OH)6
4.DG.05Kobeite-(Y)(Y,Zr)2(Ti,Fe3+)2(O,OH)7
4.DG.05Loranskite-(Y)(Y,Ce,Ca)ZrTaO6 (?)
4.DG.05Polycrase-(Y)(Y,U)(Ti,Nb)2O6
4.DG.05Tanteuxenite-(Y)(Y,Ce,Ca)(Ta,Nb,Ti)2(O,OH)6
4.DG.05Uranopolycrase(U4+,Y)(Ti,Nb)2O6
4.DG.05Yttrocrasite-(Y)(Y,Th,Ca,U)(Ti,Fe)2(O,OH)6
4.DG.10Fergusonite-(Y)-βYNbO4
4.DG.10Fergusonite-(Nd)-β(Nd,Ce)NbO4
4.DG.10Fergusonite-(Ce)-β(Ce,La,Nd)NbO4
4.DG.10Yttrotantalite-(Y)(Y,Ca,U4+,Fe2+)2(Ta,Nb)2O8
4.DG.10Beta-Fergusonite-(Nd)
4.DG.15Foordite(Sn,Pb)(Nb,Ta)2O6
4.DG.15Thoreaulite(Sn2+,Pb)(Ta,Nb)2O6
4.DG.20RaspitePb(WO4)
18.4.1Uranpyrochlore (of Hogarth 1977)(U,Ca,Ce)2(Nb,Ta)2O6(OH,F)
18.4.2Yttrocolumbite-(Y)Y(U4+,Fe2+)Nb2O8
18.4.3Yttrotantalite-(Y)(Y,Ca,U4+,Fe2+)2(Ta,Nb)2O8
18.4.4IshikawaiteU4+Fe2+Nb2O8
18.4.6Tanteuxenite-(Y)(Y,Ce,Ca)(Ta,Nb,Ti)2(O,OH)6
18.4.7Kobeite-(Y)(Y,Zr)2(Ti,Fe3+)2(O,OH)7
18.4.8Polycrase-(Y)(Y,U)(Ti,Nb)2O6
18.4.9Yttropyrochlore (of Hogarth 1977)
18.4.10Calciobetafite (of Mazzi & Munno)
18.4.11Yttrobetafite (of Hogarth 1977)
18.4.12Samarskite-(Y)(Y,Fe3+,Fe2+,U,Th,Ca)2(Nb,Ta)2O8

Other Names for Euxenite-(Y)

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Euxenite-(Y)

Reference List:
Scheerer, Th. (1840): Ueber den Euxenit, eine neue Mineralspecies. Annalen der Physik und Chemie (herausgegeben zu Berlin von J.C. Poggendorff), 50, 149-153.

Scheerer (1847), Ann. Phys.: 72: 566.

Ellsworth (1927), American Mineralogist: 12: 212.

Simpson (1928), Royal Society of Western Australia, Journal: 14: 45.

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 787-792.

Zeitschrift für Kristallographie: 152: 69-82.

Internet Links for Euxenite-(Y)

Localities for Euxenite-(Y)

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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