Keyite – A Complex Copper-Zinc-Cadmium Arsenate


  • Named after the mineral dealer Charley Key, who discovered some tiny blue crystals of this mineral on a sample of green Adamite
  • Formula: Cu3(Zn,Cd)4Cd2(AsO4)6· 2 H2O
  • Space group: I2/a (No. 15)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 11.654 Å, b = 12.780 Å, c = 6.268 Å, αγ = 90°, β = 99.11°

Picture: CC BY-SA 3.0 | Christian Rewitzer

Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • CuO4 square-planar units (blue)
  • CuO6 distorted octahedra (blue)
  • CdO6 distorted trigonal prismatic units (pink)
  • AsO4 distorted tetrahedra (green)
  • Oxygen (red)
  • Oxygen of water molecules (black(

For a 3D interactive version, see here:


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