• The colour varies between turquoise and lavender, often also electric blue specimens can be found (see the picture below)
  • Formula: NaCaCu5(AsO4)4Cl · 5 H2O
  • Space group: P21/n (No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a =  10.011, b = 19.478 Å, c = 10.056 Å, α = 90° β = 90.37°, γ = 90°

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).)

  • CuO5 and CuO4Cl tetragonal pyramids (blue)
  • CaO7 polyhedra (light blue)
  • NaO6 distorted trigonal prismatic units (yellow)
  • AsO4 tetrahedra (green)
  • Chlorine (bright green)
  • Oxygen (red)
  • Oxygen of water molecules (dark red)

For a 3D interactive version, see here:


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