The official gem of California: Benitoite


  • named after its type locality San Benito County (California)
  • it is the official state gem of California
  • Formula: BaTiSi3O9
  • Space group: P-6c2 (No. 188)
  • Crystal system: hexagonal
  • Crystal class: -6m2
  • Lattice parameters: a = b =  6.641 Å, c = 9.7579 Å, α = β = 90°, γ  120°


Picture: Didier Descouens – CC BY-SA 4.0

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


  • Ba: green, Ti: lightblue, Si: orange, O: red
  • TiO6 octahedra, SiO4 tetrahedra
  • three corner-connected SiO4 tetrahedra build a ring

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