Plášilite

Plášilite is a very rare uranium mineral with the formula Na2(UO2)(SO4)2•3H2O.[1][2] Chemically related minerals include natrozippeite, belakovskiite, meisserite, fermiite and oppenheimerite.[3][4][5][6][7] Most of these uranyl sulfate minerals were originally found in the Blue Lizard mine, San Juan County, Utah, US.[8] The mineral is named after Czech crystallographer Jakub Plášil.[2]

Plášilite
General
CategorySulfate mineral
Formula
(repeating unit)		Na(UO2)(SO4)(OH)•2H2O
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/c
Unit cella = 8.71, b = 13.84,
c = 7.05 [Å], β = 112.13° (approximated)
Identification
ColorGreenish yellow
Crystal habitprismatic
Cleavage{010} and {001}, perfect
TenacityBrittle
Mohs scale hardness2-3
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density3.73 (calculated) (approximated)
Optical propertiesBiaxal (+)
Refractive indexnα=1.56, nβ=1.58, nγ=1.61 (approximated)
Pleochroism~Colourless (X), very pale yellow (Y), pale yellow (Z)
2V angle88o (measured)
Ultraviolet fluorescenceBluish-white
Other characteristics Radioactive
References[1][2]

Association and origin

Plášilite is associated with other sulfate minerals: natrozippeite, johannite, blödite, brochantite, chalcanthite, gypsum, hexahydrite, manganoblödite, and tamarugite. Non-sulfate coexisting minerals include atacamite, calcite, dickite and gerhardtite. Plášilite is secondary in origin, being the product of weathering of the primary uranium mineral, uraninite.[1]

Crystal structure

The crystal structure of plášilite is of a new type. Its building blocks are:[1]

  • (UO2)2(SO4)2(OH)2 sheets, with a charge 2-, parallel to (010), of a phosphuranylite topology
  • edge-sharing NaO2(H2O)4 polyhedra, parallel to [001]

The sodium-bearing polyhedra link the uranyl-sulfate sheets. It terms of sheet geometry, crystal structure of plášilite is similar to that of deliensite.[1]

References
  1. Kampf, A.R., Kasatkin, A.V., Čejka, J., and Marty, J., 2015. Plášilite, Na(UO2)(SO4)(OH)·2H2O, a new uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA. Journal of Geosciences 60, 1-10
  2. "Plášilite: Plášilite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  3. "Natrozippeite: Natrozippeite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  4. "Belakovskiite: Belakovskiite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  5. "Meisserite: Meisserite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  6. "Fermiite: Fermiite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  7. "Oppenheimerite: Oppenheimerite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  8. "Blue Lizard Mine, Chocolate Drop, Red Canyon, White Canyon District, San Juan Co., Utah, USA - Mindat.org". Mindat.org. Retrieved 2016-03-10.


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