Monazite-(Ce)

 IMA-GP
Thorium 38.4.3.1
(Dana Classification Number)
(Images) 7/A.15-20
(Strunz ID)

Property Data Remarks
Named for: From the Greek word monazeis, "to be alone", in allusion to its isolated crystals and their rarity when first found, and its Cerium (rare earth) content
Alternate
    Name(s):
  • Monazite
    		•  Used as a collective name for all Monazite minerals
    Mineral Class:
    Phosphates, Arsenates and Vanadates
      Waterfree phosphates [PO4]-3 without unfamiliar anions, cations of very big size: Ca, Na and related cations
        Monazite group
    		 
    Chemical
        Formula:    		 (Ce, La, Nd, Th, Y)PO4  
    Chemical
        Composition:
    Cerium: Ce 29.17%
    Lanthanum: (La) 14.46%
    Neodymium: (Nd) 12.01%
    Oxygen: (O) 26.64%
    Phosphorus: (P) 12.89%
    Thorium: (Th) 4.83%
    		by weight
    Molecular
        Weight:    		 240.21 daltons (amu)
    Specific
        Radioactivity:

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

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    2.164 × 1003 5.85 × 10-08 0.03 3.01

    Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
    Crystalography:
    System: Monoclinic - Prismatic
    Axial Ratios: a: 0.9686
    b: 1
    c: 0.9215
    Cell Dimensions: a: 6.79 Å
    b: 7.01 Å
    c: 6.46 Å
    Z: 4
    b: 103.633°
    V: 298.82 Å3
    DenCalc: 5.34
    H-M Symbol: 2/m
    Space Group: P21/n
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 2.862 Å
    (0.8): 3.078 Å
    (0.5): 1.963 Å
    		Monazite-(Ce)
    Crystal
    Habit:
  • Typically granular or massive with no distinct form
  • Small equant to prismatic crystals with wedge-shaped terminations
  • Crystals are rarely flattened or tabular
  • Twinning is common, forming crosses and variously angled reentrant crystals
  • Crystal surfaces are often etched and pitted
    		•   
    Cleavage:
    [001] Distinct
    [010]  
    [100] Indistinct

    Cleavage often results in shards or acutely angled splinters.
    Metamiction will eliminate cleavage.
    A basal parting direction is sometimes noticeable.

    		  
    Fracture:
  • Conchoidal
  • Uneven
    		•   
    Moh's
        Hardness:    		 5 - 5.5  
    Density: 4.6 - 5.7 grams/cm3
    Color: Yellow, Yellowish-brown to Dark brown, Brown, Colorless, Greenish, or Gray white  
    Streak: White to Grayish white  
    Luster: Vitreous - Resinous - Adamantine  
    Diaphaneity: Subtransparent - Subtranslucent - Opaque  
    Pleochroism:
    (x): Colorless or Light yellow
    (y:) Colorless or Dark yellow
    (z:) Colorless or Greenish yellow
    		 
    Ultra Violet
        Fluorescence:
    Long Wave:  
    Short Wave:  
    		 
    Magnetism: Non-magnetic  
    Occurance:
    • In phosphate pegmatites as solitary crystals.
    • An accessory mineral in granite, syenite and gneiss.
    • In beach and river placer deposits.
    • A trace constituent in many ordinary igneous, metamorphic and vein filling rocks.
    		  
    Associated
        Minerals:    		 Albite, Allanite-Ce, Anatase, Aragonite, Autunite, Barite, Bastnäsite-Ce, Beryl, Biotite, Calcite, Chalcopyrite, Dolomite, Epidote, Fluorapatite, Fluorite, Galena, Goethite, Hematite, Ilmenite, 'Limonite', Magnetite, Microcline, Molybdenite, Muscovite, Orthoclase, Pyrite, Pyrrhotite, Quartz, Rutile, Schorl, Siderite, Sphalerite, Titanite, Torbernite, Uraninite, Xenotime-(Y), Zircon

    Mineral   -   > 53% of sites
    Mineral   -   > 42% of sites
    Mineral   -   > 19% of sites
    Minerals   -   Uranium & Thorium
    mineral links

    (Due to over 100 locations, only the USA sites were considered when compiling this list)
    Locations:

    Relatively common

    Monazite-(Ce) Locations
    Notes:

    Radioactive, often strongly so. This can cause crystals to be metamic.

    Monazite is technically four different minerals. Because of a lack of any great difference between them they are often considered as one mineral, 'Monazite'. The four Monazites have different chemical make up reflected in their respective names, as well as different crystal forms.

    Monazite-Ce Images

       
      Moss, Østfold, Norway