Brockite

 IMA-GP
Thorium 40.4.7.5
(Dana Classification Number)
(No Images) 7/C.29-40
(Strunz ID)

Property Data Remarks
Named for: Maurice R. Brock, U.S. Geological Survey, who supplied the first specimen
Alternate
    Name(s):
  		•  
    Mineral Class:
    Phosphates, Arsenates and Vanadates
      Water-bearing phosphates without unfamiliar anions, cations of medium and big size: Fe, Mn, Zn, Mg and Ca, (NH4)+
        Rhabdophane group
    		 
    Chemical
        Formula:    		 (Ca,Th,Ce)(PO4) · H2O  
    Chemical
        Composition:
    Calcium: (Ca) 10.90%
    Cerium: (Ce) 6.35%
    Hydrogen: (H) 0.91%
    Oxygen: (O) 36.25%
    Phosphorus: (P) 14.04%
    Thorium: (Th) 31.55%
    		by weight
    Molecular
        Weight:    		 220.66 daltons (amu)
    Specific
        Radioactivity:

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

    Specific Activity Dose Rate
    Becquerels Curies milliRADs
    per hour    		 microSieverts
    1.4133 × 1004 3.82 × 10-07 0.20 2.04

    Estimated Average Annual Exposure: 3.6 RAD (3.6 centiSieverts)
    Crystalography:
    System: Hexagonal - Trapezohedral
    Axial Ratios: a: 1
    c: 0.9169
    Cell Dimensions: a: 6.98 Å
    c: 6.4 Å
    Z: 3
    V: 270.04 Å3
    DenCalc: 4.07
    H-M Symbol: 6 2 2
    Space Group: P6222
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 3.03 Å
    (0.7): 2.83 Å
    (0.7): 4.37 Å
    		 
    Habit:
  		•  
    Cleavage: None  
    Fracture: Conchoidal  
    Moh's
        Hardness:    		 3 - 4  
    Density: 3.7 - 4.1 grams/cm3
    Color: Red-brown  
    Streak:    
    Luster: Vitreous - Greasy  
    Diaphaneity: Translucent  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:
    Long Wave:  
    Short Wave:  
    		 
    Magnetism: Non-magnetic  
    Occurance:
  • A rare accessory mineral in granite and granite pegmatites
    		•   
    Associated
        Minerals:

    Albite, Almandine, Andradite, 'Apatite', Barite, Biotite, Calcite, Cerussite, Chalcopyrite, Cryolite, Ferrocolumbite, Fluorite, Galena, Goethite, Helvite, Hematite, Ilmenite, Kaolinite, Molybdenite, Muscovite, Orthoclase, Phlogopite, Pyrite, Quartz, Schorl, Spessartine, Thorite, Titanite, Xenotime-(Y), Zircon

    Mineral   -   > 50% of sites
    Mineral   -   > 25% of sites
    Minerals   -   Uranium & Thorium
    mineral links

    		These are minerals known to be found with Brockite
    Localities:

    Very rare

    Brockite Localities
    Notes:

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

    Crystals are probably metamic.