Coffinite

 IMA-GP
Uranium 51.5.2.4
(Dana Classification Number)
(Images) 8/A.09-40
(Strunz ID)

Property Data Remarks
Named for: Reuben Clare Coffin (1886-1972), American geologist (Tulsa, Oklahoma, U.S.A.). He studied and found more than 25 uranium-vanadium deposits in south-western Colorado.
Alternate
    Name(s):
  • Coffinit
  • Coffinita
    		•   
    Mineral Class:
    Silicates
      Nesosilicates with [SiO4]-4 groups, cations of octahedral and cubic orientation [8+6]
        Zircon - Thorogummite series
    		 
    Chemical
        Formula:    		 U(SiO4)1-x(OH)4x  
    Chemical
        Composition:
    Hydrogen: (H) 0.12%
    Oxygen: (O) 19.53%
    Silicon: (Si) 7.71%
    Uranium: (U) 72.63%
    		by weight
    Molecular
        Weight:    		 327.71 daltons (amu)
    Specific
        Radioactivity:

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

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    1.30016 × 1005 3.51 × 10-06 1.70 170.19

    Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
    Crystalography:
    System: Tetragonal - Ditetragonal Dipyramidal
    Axial Ratios: a: 1
    c: 0.90187
    Cell Dimensions: a: 6.93 Å
    c: 6.25 Å
    Z: 3
    V: 300.16 Å3
    DenCalc: 5.44
    H-M Symbol: 4/m 2/m 2/m
    Space Group: I41/amd
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 3.47 Å
    (1): 4.66 Å
    (0.7): 2.64 Å
    		 
    Habit:
  • Crusts
  • Massive veins
  • Interstitial fill and granuals
    		•   
    Cleavage: None  
    Fracture: Brittle  
    Moh's
        Hardness:    		 5 - 6  
    Density: 5.1 (variable) grams/cm3
    Color: Black (some fracture faces may apear grayish-black)  
    Streak: Grayish black to black  
    Luster: Dull to Subadamantine  
    Diaphaneity: Subtranslucent to Opaque  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:    		 Non-Fluorescent

    (The specimen's sandstone matrix, containing the Coffinite, is also non-fluroescent)    		 (One Specimen Examined)
    Magnetism: Non-magnetic  
    Occurance:
  • Low temperature hydrothermal deposition in sedimentary rock (sandstone)
  • Replacement of vegetal material in sandstone.
    		•   
    Associated
        Minerals:

    Arsenopyrite, Autunite, Barite, Calcite, Chalcocite, Chalcopyrite, Covellite, Dolomite, Fluorite, Galena, Goethite, Gypsum, Hematite, Malachite, Marcasite, Montroseite, Meta-Autunite, Pyrite, Quartz, Safflorite, Skutterudite, Sphalerite, Tennantite, Torbernite, Uraninite, Uranophane

    Mineral   -   > 67% of sites
    Mineral   -   > 50% of sites
    Mineral   -   > 25% of sites
    Minerals   -   Uranium & Thorium
    mineral links

    Often found with carbonatious material.

    		 These are minerals known to be found with Coffinite
    Localities:

    Somewhat rare

    Coffinite Localities
    Notes:

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

    Crystals are probably metamic.

    Coffinite Images

    Specimen #1
    (001aa) (001a) (001b)
    Temple Mountain Consolidated Mine,
    Emery Co., Utah, U.S.A.

    Specimen Notes

    Occurrence - The Coffinite occurs in an unremarkable sandstone. The sandstone grains are sharp, showing at most only slight rounding from polishing by the action of either wind or water.

    The Coffinite content of the specimen changes the sandstone's usual grayish-tan color to a charcoal black. Under microscope examination, as seen in images (001a) and (001b), the sandstone's original color can be seen.

    Coffinite, contains no hot radicals (anions having a -1 valence), but it is not a Uranyl mineral, and therefore is exempt from the hot radicals theory. Coffinite occurs in direct contact with the silica of the sandstone.

    Crystals - No crystals can be seen in the specimen.

    Appearence - The Coffinite occurs as small grains filling the interstities between the sand grains of the sandstone. It acts as an aditional cement bonding the quartz grains together.

    Diaphaneity - The bright surfaces of the Coffinite grains can give the illusion of slight translucency, but the opaque nature of the thin films on light colored quartz grains betrays its real opacity.

    Luster - Vitreous. The Coffinite often gives the appearence of broken black glass, but also as a viteous black coating on some quartz grains.

    Fracture - The broken black glass appearence of Coffinite indicates its fracture to be more conchoidal rather than brittle.

    Radioactivity - The low level of radioactivity indicates a rather low degree of Coffinite content within the specimen. This low Coffinite content is borne out by microscopic examination.

    Specimen Physical Properties
    Size   cm   cm   cm
    Weight: 73.38 grams    
    g-Radiation Level: 72 cmp 0.72 msieverts background: 22 cpm