Steacyite

 IMA-A 1981-E
Thorium 63.1.1.1
(Dana Classification Number)
(No Images) 8/E.10-30
(Strunz ID)

Property Data Remarks
Named for: Harold R. Steacy, Curator, National Mineral Collection, Geological Survey of Canada
Alternate
    Name(s):
  • Desourdyite
    		•   
    Mineral Class:
    Silicates
      Cyclosilicates, double quadruplet rings [Si8O20]8-
        Ekanite - Steacyite series
    		 
    Chemical
        Formula:    		 K1-x(Ca,Na,Mn)2ThSi8O20

    [x = 0.2 to 0.4]    		  
    Chemical
        Composition:
    Calcium: (Ca) 3.40%
    Manganese: (Mn) 1.33%
    Oxygen: (O) 37.98%
    Potassium: (K) 2.84%
    Silicon: (Si) 27.21%
    Sodium: (Na) 1.95%
    Thorium: (Th) 25.29%
    		by weight
    Molecular
        Weight:    		 825.70 daltons (amu)
    Specific
        Radioactivity:

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

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    1.1332 × 1004 3.06 × 10-07 0.17 16.67

    Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
    Crystalography:
    System: Tetragonal - Ditetragonal Dipyramidal
    Axial Ratios: a: 1
    c: 1.94854
    Cell Dimensions: a: 7.58 Å
    c: 14.77 Å
    Z: 2
    V: 848.63 Å3
    DenCalc: 3.23
    H-M Symbol: 4/m 2/m 2/m
    Space Group: P4/mcc
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 3.38 Å
    (0.9): 5.22 Å
    (0.9): 7.32 Å
    		 
    Habit:
  • Radial
  • Massive
    		•   
    Cleavage: None  
    Fracture: Brittle  
    Moh's
        Hardness:    		 5  
    Density: 2.95 grams/cm3
    Color: Brown  
    Streak: White  
    Luster: Vitreous - Dull  
    Diaphaneity: Translucent  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:
    Long Wave:  
    Short Wave:  
    		 
    Magnetism: Non-magnetic  
    Occurance:
  • In cavities in pegmatite veins in nepheline syenite
    		•   
    Associated
        Minerals:

    Aegirine, Albite, Analcime, Andradite, Arfvedsonite, Astrophyllite, Biotite, Calcite, Datolite, Eudialyte, Fluorapatite, Fluorite, Galena, Hedenbergite, Leucosphenite, Microcline, Miserite, Muscovite, Nepheline, Neptunite, Pectolite, Polylithionite, Pyrochlore, Quartz, Schorl, Sphalerite, Stillwellite-(Ce), Titanite, Wollastonite

    Minerals   -   Uranium & Thorium
    mineral links

    		These are minerals known to be found with Steacyite
    Locations:

    Very rare

    Steacyite Locations
    Notes:

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

    Crystals are probably metamic.