Chibaite: Properties and Occurrences

Chibaite is a rare silicate mineral. It is a silica clathrate with formula SiO2·n(CH4, C2H6, C3H8,i-C4H10) (n = 3/17 (max)). It is a silica mineral discovered from Boso Peninsula, Japan. The mineral is cubic (diploidal class, m3) and the silica hosts or traps various hydrocarbon molecules.

Chibaite was first described for specimens collected from Arakawa, Minamibōsō, Chiba Prefecture, Honshu Island, Japan. The mineral was approved by the IMA in 2009.

General information

  • Formula: SiO2n(CH4, C2H6, C3H8,i-C4H10) (n = 3/17 (max))
  • Color: colorless
  • Lustre: Vitreous
  • Hardness: 6½ – 7
  • Specific Gravity: 1.933 (Calculated)
  • Crystal System: Isometric

Physical Properties

  • Lustre: Vitreous
  • Hardness: 6½ – 7 on Mohs scale
  • Cleavage: None Observed
  • Density: 1.933 g/cm3 (Calculated)

The chibaite structure is preserved throughout the whole pressure range. The deviation from regular shift and appearance of new bands in the lattice spectrum is observed at about 1.2 and 3.5 GPa. As concerns, the guest hydrocarbon molecules, the high-frequency shifts of their C–C and C–H bands are almost monotonic within the whole pressure range, showing only slight bends at 1.2 and 3.5 GPa.


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