Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi
To reveal the species of gem-grade red garnets with similar colors, especially the mechanisms underlying their subtle color differences, a series of tests, including conventional gemological tests, X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ra...
Saved in:
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2022-01-01
|
| Series: | Journal of Spectroscopy |
| Online Access: | http://dx.doi.org/10.1155/2022/1638042 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832552939413045248 |
|---|---|
| author | Ming Li |
| author_facet | Ming Li |
| author_sort | Ming Li |
| collection | DOAJ |
| description | To reveal the species of gem-grade red garnets with similar colors, especially the mechanisms underlying their subtle color differences, a series of tests, including conventional gemological tests, X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy, were performed on gem-grade red garnets mined from Malawi. The results demonstrated that the color difference is not caused by the difference in species, and both the purplish-red and maroon-red garnets were magnesium-aluminum garnets (pyrope). They both contained the transition metal ions Fe2+, Mn2+, Fe3+, and Cr3+, with Fe2+ and Mn2+ occupying crystal site A and Fe3+ and Cr3+ occupying crystal site B. Cr3+ absorption peaks were observed at 367 and 690 nm; Fe3+ absorption peaks were observed at 502, 528, and 570 nm; and Mn2+ absorption peaks were observed at 400, 423, and 460 nm, which contributed to their respective colors. However, while the maroon-red pyrope had a larger Fe2+/Fe3+ ratio than the purplish-red pyrope, it lacked Mn2+ ions, which is the cause of the color difference between the two pyrope garnets. To date, the study of color differences in red garnets remains a major controversial topic. This study proposed an innovative spectroscopic approach, particularly the combination of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy, thus providing a novel methodology for investigating color differences in red garnets. |
| format | Article |
| id | doaj-art-b6aef13390ec4bec8233b1b6625e0c43 |
| institution | Kabale University |
| issn | 2314-4939 |
| language | English |
| publishDate | 2022-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Journal of Spectroscopy |
| spelling | doaj-art-b6aef13390ec4bec8233b1b6625e0c432025-02-03T05:57:30ZengWileyJournal of Spectroscopy2314-49392022-01-01202210.1155/2022/1638042Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from MalawiMing Li0Jewelry InstituteTo reveal the species of gem-grade red garnets with similar colors, especially the mechanisms underlying their subtle color differences, a series of tests, including conventional gemological tests, X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy, were performed on gem-grade red garnets mined from Malawi. The results demonstrated that the color difference is not caused by the difference in species, and both the purplish-red and maroon-red garnets were magnesium-aluminum garnets (pyrope). They both contained the transition metal ions Fe2+, Mn2+, Fe3+, and Cr3+, with Fe2+ and Mn2+ occupying crystal site A and Fe3+ and Cr3+ occupying crystal site B. Cr3+ absorption peaks were observed at 367 and 690 nm; Fe3+ absorption peaks were observed at 502, 528, and 570 nm; and Mn2+ absorption peaks were observed at 400, 423, and 460 nm, which contributed to their respective colors. However, while the maroon-red pyrope had a larger Fe2+/Fe3+ ratio than the purplish-red pyrope, it lacked Mn2+ ions, which is the cause of the color difference between the two pyrope garnets. To date, the study of color differences in red garnets remains a major controversial topic. This study proposed an innovative spectroscopic approach, particularly the combination of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy, thus providing a novel methodology for investigating color differences in red garnets.http://dx.doi.org/10.1155/2022/1638042 |
| spellingShingle | Ming Li Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi Journal of Spectroscopy |
| title | Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi |
| title_full | Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi |
| title_fullStr | Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi |
| title_full_unstemmed | Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi |
| title_short | Spectroscopic Study on the Species and Color Differences of Gem-Quality Red Garnets from Malawi |
| title_sort | spectroscopic study on the species and color differences of gem quality red garnets from malawi |
| url | http://dx.doi.org/10.1155/2022/1638042 |
| work_keys_str_mv | AT mingli spectroscopicstudyonthespeciesandcolordifferencesofgemqualityredgarnetsfrommalawi |