Thaumasite – a suprising mineral


  • first described in 1878 in Sweden and named from the Greek, “thaumazein”, to be surprised, in reference to its unusual composition with carbonate, sulfate and hydroxysilicate anions
  • Formula: Ca3Si(OH)6(CO3)(SO4)
  • Space group: P63 (No. 173)
  • Crystal system: hexagonal
  • Crystal class: 6
  • Lattice parameters: ab = 11.0538 Å, c = 10.4111 Å, α = β = 90°, γ = 120°

Picture: Rob Lavinsky|  | CC BY-SA-3.0

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).)

  • CaO8 polyhedra (blue)
  • SiO6 octahedra (orange)
  • SOtetrahedra (yellow)
  • COtrigonalplanar coordination (gray)
  • Oxygen (red)
  • Hydrogen (white)

For a 3D interactive version on sketchfab, see here:


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