Monazite-(Sm)

 IMA-A 2001-001
Thorium 38.4.3.7
(Dana Classification Number)
(No Images) 7/A.15-
(Strunz ID)

Property Data Remarks
Named for: From the Greek word monazeis, "to be alone", in allusion to its isolated crystals and rarity when first found, and its Samarium (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:    		 SmPO4  
    Chemical
        Composition:
    Calcium: (Ca) 1.81%
    Cerium: (Ce) 9.50%
    Gadolinium: (Gd) 14.21%
    Neodymium: (Nd) 6.52%
    Oxygen: (O) 26.03%
    Phosphorus: (P) 12.60%
    Samarium: (Sm) 13.59%
    Thorium: (Th) 15.73%
    		by weight
    Molecular
        Weight:    		 221.25 daltons (amu)
    Specific
        Radioactivity:

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

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    7.065 × 1003 1.91 × 10-07 0.10 9.77

    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: 6.725 Å
    b: 6.936 Å
    c: 6.448 Å
    Z: 4
    b: 104.02°
    V: 291.80 Å3
    DenCalc: 5.04
    H-M Symbol: 2/m
    Space Group: P21/n
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 3.065 {120} Å
    (0.9): 2.857 {112}, {012} Å
    (0.8): 4.162 {111} Å
    (0.7): 3.264 {200} Å
    (0.5): 4.647 {011} Å
    (0.4): 3.492 {111}, {020} Å
    (0.4): 5.19 Å
    		 

    Habit:
  • Micaceous, sub-hedral crystals
  • Crystal surfaces are often etched and pitted
    		•   
    Cleavage:
    [???] Good

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

    		  
    Fracture:
  • Brittle


    • Metamiction increases the degree of conchoidal fracture    		  
    Moh's
        Hardness:    		 5 - 5.5  
    Density: 4.6 - 5.7   (Expected, not measured) grams/cm3
    Color: Yellowish  
    Streak: White  
    Luster: Vitreous - Greasy  
    Diaphaneity: Translucent to Transparent  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:
    Long Wave: None
    Short Wave: None
    		 
    Magnetism: Non-magnetic  
    Occurance:
    • Lepidolite-subtype granitic pegmatite within the Greer Lake intrusion of pegmatitic leucogranite
    		  
    Associated
        Minerals:    		  
    Locations:

    Extremely rare

    Monazite-(Sm) 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 makeup reflected in their respective names, and their different crystaline forms.