Miscellaneous olivines

Crystal field spectra of a chromium-bearing forsterite yielded bands at 23,500 and 16,900 cm 1 (Scheetz and White, 1972), indicating a CFSE of 20,280 cm-1 for Cr3+ in the olivine structure. Additional broad, asymmetric bands centred at 11,800 and 6,400 to 6,700 cm 1 were attributed to crystal field transitions in Cr2+ (Scheetz and White, 1972 Bums, 1974). Although EPR measurements of forsterite show slight enrichments of Cr3 in the Ml sites (Rager, 1977), polar- 

The crystal field spectrum of Fe2Si04 spinel contains a broad, slightly asymmetric band centred around 11,430 cm-1 (Mao and Bell, 1972b Bums and Sung, 1978), leading to the crystal field parameters for Fe2+ of 

These values are significantly higher than the values estimated for Fe2+ in the olivine Ml and M2 sites (eqs (5.2) and (5.3)). 

The reflectance spectrum of Ni2Si04 spinel contains intense bands with absorption maxima of 9,150 cm-1, 14,780 cm-1 and 22,550 cm-1 at atmospheric pressure (Yagi and Mao, 1977). These led to initial estimates of the crystal field parameters for Ni2+ in silicate spinel of A0 = 9.,150 cm-1 and CFSE = 10,980 cm-1. However, there is also a prominent shoulder in the reflectance spectra around 8,000 cm-1 attributable to trigonal distortion of the octahedral site in the spinel structure (Bums, 1985a). This led to revised estimates for Ni2+ in Ni2Si04 spinel of 

Mineral or Cation Positions of absorption bands 4 CFSE Sources 

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