The official gem of California: Benitoite

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°

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Picture: Didier Descouens – CC BY-SA 4.0

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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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