Keyite

Keyite

Keyite on adamite (greenish)
General
Category Arsenate minerals
Formula
(repeating unit)		 Cu2+
3Zn
4Cd
2(AsO
4)6 · 2H
2O
Strunz classification 08.CA.50
Crystal symmetry 2/m
Unit cell a = 11.654(3) Å, b = 12.780(5) Å, c = 6.840(3) Å, β = 99.11°
Identification
Formula mass 1,520.19 g
Color azure/blue
Crystal habit prismatic, tabular
Crystal system monoclinic – prismatic
Cleavage good (001) cleavage
Mohs scale hardness 3.5 - 4
Streak light blue
Diaphaneity translucent
Density 5.106g/cm3
Optical properties biaxial
Refractive index nα = 1.800, nβ, and nγ = 1.870
Birefringence 0.070
Pleochroism x: pale blue, y: greenish blue, z: deep blue
References

[1] [2]

[3]

Keyite is a mineral with the chemical formula Cu2+
3Zn
4Cd
2(AsO
4)6 · 2H
2O.[4] The name comes from Charles Locke Key (born 1935), an American mineral dealer who furnished its first specimens.[5] Keyite is monoclinic-prismatic, meaning its crystal form has three unequal axes, two of which have 90° angles between them and one with an angle less than 90°.[6] Keyite belongs to the biaxial optical class, meaning it has more than one axis of anisotropy (optic axis), in which light travels with zero birefringence, and three indices of refraction, nα = 1.800, nβ, and nγ = 1.870.[7][8] Being a very rare cadmium copper arsenate, keyite is only found in Tsumeb, Namibia in the Tsumeb mine, a world famous copper mine known for its abundance of rare and unusual minerals.[9]

References

  1. ↑ Fleischer, M., Cabri, L.J., and Pabst, A. (1977) New Mineral Names. American Mineralogist, 62, 1259.
  2. ↑ Cooper, M.A. and Hawthorne, F.C. (1996) The crystal structure of keyite, Cu2+
    3    Zn
    4    Cd
    2    (AsO
    4    )6(H
    2    O)2, an oxysalt mineral with essential cadmium. Canadian Mineralogist, 34, 623-630.
  3. ↑ http://webmineral.com/data/Keyite.shtml. Accessed 2 December 2010.
  4. ↑ Fleischer, M., Cabri, L.J., and Pabst, A. (1977) New Mineral Names. American Mineralogist, 62, 1259.
  5. ↑ Cooper, M.A. and Hawthorne, F.C. (1996) The crystal structure of keyite, Cu2+
    3    Zn
    4    Cd
    2    (AsO
    4    )6(H
    2    O)2, an oxysalt mineral with essential cadmium. Canadian Mineralogist, 34, 623-630.
  6. ↑ Cooper, M.A. and Hawthorne, F.C. (1996) The crystal structure of keyite, Cu2+
    3    Zn
    4    Cd
    2    (AsO
    4    )6(H
    2    O)2, an oxysalt mineral with essential cadmium. Canadian Mineralogist, 34, 623-630.
  7. ↑ http://www.mindat.org/min-2191.html. Accessed 2 December 2010.
  8. ↑ http://webmineral.com/data/Keyite.shtml. Accessed 2 December 2010.
  9. ↑ Cooper, M.A. and Hawthorne, F.C. (1996) The crystal structure of keyite, Cu2+
    3    Zn
    4    Cd
    2    (AsO
    4    )6(H
    2    O)2, an oxysalt mineral with essential cadmium. Canadian Mineralogist, 34, 623-630.


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