Study on the Unique Mineral Microstructure of Seawater Cultured Gray Akoya Pearl by SEM, FTIR and Reflection Spectroscopy

FANG Biao; YAN Xue-jun; SUN Qing; WU Jing-yi; LI Shu-hua; YAN Jun

doi:10.15898/j.cnki.11-2131/td.201908200124

2021 Vol. 40, No. 1

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Article navigation > Rock and Mineral Analysis > 2021 > 40(1): 42-49

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FANG Biao, YAN Xue-jun, SUN Qing, WU Jing-yi, LI Shu-hua, YAN Jun. Study on the Unique Mineral Microstructure of Seawater Cultured Gray Akoya Pearl by SEM, FTIR and Reflection Spectroscopy[J]. Rock and Mineral Analysis, 2021, 40(1): 42-49. doi: 10.15898/j.cnki.11-2131/td.201908200124

Citation:

FANG Biao, YAN Xue-jun, SUN Qing, WU Jing-yi, LI Shu-hua, YAN Jun. Study on the Unique Mineral Microstructure of Seawater Cultured Gray Akoya Pearl by SEM, FTIR and Reflection Spectroscopy[J]. Rock and Mineral Analysis, 2021, 40(1): 42-49. doi: 10.15898/j.cnki.11-2131/td.201908200124

Study on the Unique Mineral Microstructure of Seawater Cultured Gray Akoya Pearl by SEM, FTIR and Reflection Spectroscopy

1.
Zhejiang Fangyuan Testing Group Co., LTD, Hangzhou 310013, China
2.
College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014, China
3.
Wenzhou Institute of Science and Technology, Zhejiang University of Technology, Wenzhou 325024, China

More Information

Corresponding author: YAN Jun, yanj_zjut@163.com

Received Date: 20 August 2019

Revised Date: 31 January 2020

Accepted Date: 13 May 2020

Publish Date: 28 January 2021

Abstract

Abstract

BACKGROUND
Seawater cultured gray Akoya pearls have become popular as jewelry in the recent years. In the early stage, some research focused mainly on investigating the cultured environment of seawater or freshwater pearls, element occurrence characteristics of each structural unit, irradiation treatment and the identification method of irradiated pearls.
OBJECTIVES
To further study the gemological characteristics and fine microstructure of a type of gray pearl with a white nucleus.
METHODS
Ultraviolet-visible reflection spectrum, micro-infrared spectrum and scanning electron microscope methods were used.
RESULTS
A brown transition layer of organic matter between the nacre and nucleus was discovered, which measures several microns in thickness. A layer with no fixed morphology composed of calcite and vaterite in the nacre near the brown transition layer was also discovered. Quasi plates of aragonite exist in the nacre near the surface of the pearl. The morphology of these aragonite tablets in the middle area of the nacre was more regular, the thickness of individual aragonite plate gradually decreased in the direction from the nucleus to the surface of the pearls. The reflectance spectrum of the entire pearl surface was consistent with the spectral characteristics of the outer single nacre. The brown transition layer had no direct effect on the UV-Vis reflectance spectrum of the entire pearl. Therefore, whether or not the brown transition layer affected the gray appearance of the pearl needs further discussion.
CONCLUSIONS
The research work has important guiding significance for the coloring mechanism of gray Akoya pearls and the identification of the formation attributes. It can also aid in the recognition of the fine structure and mineralization characteristics of pearls with a thin layer of nacre of 0.3mm to 0.6mm.
- gray pearl /
- microstructure /
- transition layer /
- nacre /
- UV-Vis reflectance spectroscopy /
- scanning electron microscope

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References

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