Euxenite-(Y)

 IMA-GP
Uranium   (trace)
Thorium   (trace)		 8.3.8.2
(Dana Classification Number)
(Images) 4/D.19-40
(Strunz ID)

Property Data Remarks
Named for: From Greek for "friendly to strangers," due to its rare earth element content
Alternate
    Name(s):
  • Euxenite
    		•   
    Mineral Class:
    Oxides
      Oxides with metal: (metal:oxygen = 1:2)
    (MO2 and related compounds)
        Polycrase-(Y) - Loranskite-(Y) series
    		 
    Chemical
        Formula:    		 (Y,Er,Ce,U,Th,Pb,Ca)(Nb,Ta,Ti)2(O,OH)6

    (Uranium is often a minor constituent).    		  
    Chemical
        Composition:
    Calcium: (Ca) 2.04%
    Cesium: (Ce) 3.57%
    Niobium: (Nb) 33.16%
    Oxygen: (O) 24.47%
    Tantalum: (Ta) 18.45%
    Titanium: (Ti) 2.44%
    Yttrium: (Y) 15.86%
    Thorium: (Th) (trace)
    Uranium: (U) (trace)
    		by weight
    Molecular
        Weight:    		 392.28 daltons (amu)
    Specific
        Radioactivity:

    (All radiation is for a 1 gram, fully aged specimen)

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    80 2.16 × 10-09 0.0 0.01

    Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
    Crystalography:
    System: Orthorhombic - Dipyramidal
    Axial Ratios: a: 0.3788
    b: 1
    c: 0.3545
    Cell Dimensions: a: 5.52 Å
    b: 14.57 Å
    c: 5.166 Å
    Z: 3
    V: 415.48 Å3
    DenCalc: 4.70
    H-M Symbol: 2/m 2/m 2/m
    Space Group: Pcan
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 2.99 Å
    (0.4): 2.95 Å
    (0.4): 3.66 Å
    		 
    Habit:
  • Short thick prismatic crystals flattened on the {010} plane
  • Large crystals common, often aligned to each other
  • Granular
  • Massive
  • Often metamict with high uranium content
    		•   
    Cleavage: None  
    Fracture:
  • Brittle
  • Conchoidal
    		•   
    Moh's
        Hardness:    		 5.5 - 6.5  
    Density: 4.6 - 5.9 grams/cm3
    Color: Dark brown to Black, with a tint of Yellow or Green  
    Streak: Light brown to Reddish-brown, Gray  
    Luster:
  • Metallic to vitreous
  • Greasy (oily)
    		•   
    Diaphaneity: Translucent to opaque  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:    		 Non-fluorescent  
    Magnetism: Non-magnetic  
    Occurance:
  • Uranium-Thorium-REE granitic pegmatites
    		•   
    Associated
        Minerals:

    Albite, 'Albite-Anorthite Series', Allanite-(Ce), Anatase, 'Apatite', Beryl, Betafite, Biotite, Bismuthinite, Calcite, 'Chlorite Group', 'Columbite', Epidote, 'Fergusonite', Fluorite, 'Garnet Group', Hematite, 'Hornblende', Ilmenite, Kaolinite, Magnetite, Microcline, Molybdenite, Monazite-(Ce), Muscovite, 'Oligoclase', Orthoclase, Pyrite, Pyrochlore, Quartz, Samarskite, Titanite, 'Tourmaline Group', Uraninite, Uranophane, Xenotime-(Y), Zircon

    Mineral   -   > 44% of sites
    Mineral   -   > 32% of sites
    Mineral   -   > 14% of sites
    Minerals   -   Uranium & Thorium
    mineral links

    		These are minerals known to be found with Euxenite-(Y)
    Localities:

    Uncommon

    Euxenite-(Y) Localities

    (Relatively common in Scandinavian countries)
    Notes:

    Strongly radioactive a- and b-particles, g-rays.

    Sometimes used as an ore of Tantalum, Terbium and Thulium.

    History: Euxenite-(Y) was first described in 1870 by Scheerer. Euxenite-(Y) played an important role in the discovery of the element Scandium, the 21st element in the periodic table. Scandium was discovered by Lars Nilson in 1878 in the minerals Euxenite and Gadolinite (L. Scandia, Scandinavia). By processing 10 kg of Euxenite-(Y) and other residues of rare-earth minerals, Nilson was able to prepare about 2g of highly pure scandium oxide.

    Euxenite-(Y) Images

    Specimen #1
    (001a) (001b) (001c)

         		 (Euxenite-(Y) heavily coated with Zircon)
    (001d) (001e) (001f) (001g)
    Manakara District, Madagascar

    Specimen Notes

    Occurrence -  

     

    Crystals -  

     

    Appearence -  

    Diaphaniety -

    Luster -

     

      -  

     

    Specimen Physical Properties
    Size   cm   cm   cm
    Weight: x grams    
    g-Radiation Level:   cmp   msieverts background: 20 cpm
           
     

    Specimen #2
    (002a) (002b) (002c) (002d)

     
     
    (002e) (002f) (002g)
    Lac Recluse, Papineau Co., Portland Township, St-Pierre-de-Wakefield, Québec, Canada

    Specimen Notes

    Occurrence - The Euxenite-(Y) occurs with microcline, and the fragment seen in images (002b) thru (002d) appears to be the variety Amazonite. Green Microcline occurs as a wide vein elsewhere in the specimen.

    The greenish coating on many surfaces, best seen in image (002e), is believed to also be microcline. Many of the 'freshly' fractured surfaces show a light to heavy coating of this mineral.

    Crystals - The natural faces of several intergrown crystals can be seen in images (002a) thru (002d), and (002f). Only three or four facettes of each crystal can be seen due to intergrowth. The intergrowth of three crystals in image (002f) produces a non-right angle inside corner.

    The crystal surfaces displayed by the specimen all appear to be aligned to each other. This is seen in most crystals of Euxenite-(Y).

    Appearence - The specimen presents two appearences, one the natural crystal surface, the other the fratured surface of the mineral's interior.

    Diaphaniety - The mineral is essentially opaque except in limited areas. One such area, in the center of the right half of image (002e), gives a golden reflection similar in color to pyrite. This reflection also gives the impresion of depth, and not being a surface reflection, though it is highly dependant on the orientation of the light. Some thin sections also show a very slight light transmission.

    Luster - The natural surface of the crystals have an earthy luster, similar to slate. This appears to have no relationship to the microcline film covering many areas of the specimen. There is also a faint grain to the surface oriented with the long axis of the crystals. This surface also is quite uneven, almost lumpy, as can be seen in image (001c).

    Fracture - The broken surface of the Euxenite-(Y) is vitreous and very reflective where free of Microcline coating. The Microcline coating does not appear to adhere well to the Euxenite-(Y) as it is chipped off in places.

    Fracture - The fracture of the Euxenite-(Y) specimen is brittle and choncoidal. It may be mistaken for a black Obsidian, only Euxenite-(Y) has a density twice that of Obsidian (

      -  

     

    Radioactivity - The specimen is extremely radioactive, many times more so than can be accounted for in the Chemical Composition section above. Either the Euxenite-(Y) has much more uranium in it than usual, or a large portion of the specimen is Uraninite.

    Specimen Physical Properties
    Size 6.6 cm 4.1 cm 2.5 cm
    Weight: 151.88 grams    
    g-Radiation Level:
        (at 2.54 cm from g-m counter)
        (30 minute average)    		 2182 cmp
    2251 cpm max
    2086 cpm min    		 2.182 msieverts background: 20 cpm