Hellandite-(Ce)

 IMA-8F.36-15
Uranium     (Trace)
Thorium     (Trace)		 54.2.2.4
(Dana Classification Number)
(No Images) A 2001-019
(Strunz ID)

Property Data Remarks
Named for: Amund Theodor Helland (1846-1918), geologist, Oslo, Norway
Alternate
    Name(s):
  • IMA2000-F
    		•   
    Mineral Class:
    Silicates
      Inosilicates, - complex chain structure.
    Cylindric chains and others
        Caysichite-(Y) - Tadzhikite-(Ce) series
    		 
    Chemical
        Formula:    		 (Ca,REE)8(Th,U,Y,REE)4(Al,Fe3+,Ti)2(OH)4(Be,Li)4(Si8B8O44)  
    Chemical
        Composition:
    Aluminum: (Al)   2.42%
    Boron: (B)   3.88%
    Calcium: (Ca)   10.79%
    Cerium: (Ce)   25.15%
    Hydrogen: (H)   0.14%
    Fluorine: (F)   0.85%
    Oxygen: (O)   33.75%
    Silicon: (Si)   10.08%
    Thorium: (Th)   (Trace)
    Uranium: (U)   (Trace)
    REE2O3
        Lanthanum
        Neodymium
        Praeseodymium
        Samarium    		  
    (La)
    (Nd)
    (Pr)
    (Sm)    		 | 
    |
    |
    |
    |    		 12.93%
    		by weight
    Molecular
        Weight:    		 1,114.02 daltons (amu)
    Specific
        Radioactivity:

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

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    854 2.31 × 10-08 0.01 0.13

    Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
    Crystalography:
    System: Monoclinic - Prismatic
    Axial Ratios: a: 4.0185
    b: 1
    c: 2.1683
    Cell Dimensions: a: 19.0680 Å
    b: 4.7450 Å
    c: 10.2890 Å
    Z: 1
    b: 111.18°
    V: 868.4 Å3
    DenCalc: 3.69
    H-M Symbol: 2/m
    Space Group: P2/a
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 2.652 Å
    (0.73): 2.635 Å
    (0.56): 2.855 Å
    (0.5): 3.238 Å
    (0.49): 1.905 Å
    (0.41): 1.901 Å
    (0.35): 2.916 Å
    		 
    Habit:
  • Euhedral Crystals
  • Microscopic Crystals
    		•   
    Cleavage:
    [001]  
    [010]  
    [100]  
    		 
    Fracture:    
    Moh's
        Hardness:    		 5.5 - 6  
    Density:   grams/cm3
    Color: Pale brown, Light green, Yellow-green  
    Streak:    
    Luster: Vitreous  
    Diaphaneity: Transparent  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:
    Long Wave:  
    Short Wave:  
    		 
    Magnetism: Non-magnetic  
    Occurance:
  • Occurs in miarolitic cavities in a volcanic ejectum within an explosive breccia
    		•   
    Associated
        Minerals:

    Hellandite-(Ce) is the only mineral listed for its only known location.

    		  
    Localities

    Rare

    Hellandite-(Ce) Localities
    Notes:

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

    Crystals are probably metamic.