Research Article
Gemological and Spectral Characteristics of Gem-Quality Blue Gahnite from Nigeria
Table 4
Shift (cm−1) comparison of the spinel Raman mode.
| | Mode | Gahnite | ZnAl2O4 crystals | Natural blue spinel (Fe, Zn chromogenic) | Natural blue spinel (Co chromogenic) | Natural pink spinel (Cr chromogenic) | Synthetic spinel | | This work | [15] | [16] | [14] | [17] | [16] |
| | T2g(1) | — | 194 | 312 | 312 | 312 | 311 | | Eg | 418 | 427 | 406 | 407 | 407 | 402 | | T2g(2) | 508 | 513 | — | — | — | — | | T2g(3) | 660 | 655 | 664 | 666 | 667 | 673 | | A1g | — | 775 | 766 | 767 | 769 | 766 | | Others | — | — | — | — | N3:720 | 226, 723 |
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