Artificial coloration of ancient agate beads: a mineralogical study

IF 2.6 1区艺术学 Q2 CHEMISTRY, ANALYTICAL

Heritage Science Pub Date : 2023-09-13 DOI:10.1186/s40494-023-01039-7

Xiaoguang Li, Haozhong Xue, Xinhua Wu, Dahai Qin, Daiming Chen, Jiangyan Yuan, Zihua Tang

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引用次数: 0

Abstract

Abstract The process of staining was frequently employed to enhance or alter the color of agate beads in ancient times. One of the key challenges in studying ancient beads is comprehending the intricate techniques employed to color agate stones. An understanding of the staining mechanism from a mineralogical standpoint offers insights into the level of technological advancement in different civilizations. In this study, the mineral structure of eight ancient agate beads from Xinjiang Uygur Autonomous Region, NW China, was analyzed using Micro X-ray fluorescence (µXRF), Raman spectroscopy, Scanning Electron Microscope (SEM), and Fourier Transform Infrared (FTIR) techniques. The color, transparency, mineral phase, and surface roughness of the beads were examined, revealing variations ranging from colorless to light violet to dark violet. Raman and FTIR spectroscopy were employed to determine the SiO 2 phase and the changes in optical characteristics of agate beads after artificial staining. The black color of the beads was formed by carbon penetration, while the red color was produced by heating. The coexistence of α-quartz and moganite phases in the red, the dark red, the black, the idiochromatic white and the part translucent zones of the ancient beads was confirmed by the 464 cm −1 peak of α-quartz and the 502 cm −1 peak of moganite phase. The analyzed red, the dark red, the black, the idiochromatic white and the part translucent zones exhibited remarkably similar FTIR spectral features, with two prominent bands at ~ 1097 and ~ 1187 cm −1 , as well as two weak bands at 798 and 778 cm −1 , indicating the presence of moganite and α-quartz in the unetched ancient beads. In contrast to the idiochromatic white appearance of natural agate, the scattered white coloration in etched beads was generated by an etching reaction. Both Raman and FTIR spectroscopy indicated the absence of moganite in etched beads, indicating that the scattered white color was produced by the loss of moganite and a portion of α-quartz, resulting in a rough surface.

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古玛瑙珠的人工染色:矿物学研究

摘要古代常用染色工艺来增强或改变玛瑙珠的颜色。研究古代珠子的关键挑战之一是理解玛瑙宝石上色的复杂技术。从矿物学的角度对染色机制的理解有助于了解不同文明的技术进步水平。本文采用微x射线荧光(µXRF)、拉曼光谱(Raman spectroscopy)、扫描电镜(SEM)和傅里叶变换红外(FTIR)等技术对新疆8颗古玛瑙珠的矿物结构进行了分析。检测了珠子的颜色、透明度、矿物相和表面粗糙度，揭示了从无色到浅紫色到深紫色的变化。采用拉曼光谱和傅里叶红外光谱测定了人工染色后玛瑙珠的sio2相及光学特性的变化。珠子的黑色是由碳渗透形成的，而红色是由加热产生的。α-石英峰为464 cm−1，莫干石相峰为502 cm−1，证实了α-石英相与莫干石相在古珠珠的红色、深红色、黑色、独特色白色及部分半透明区共存。分析的红色、暗红色、黑色、专色白色和部分半透明区域的FTIR光谱特征非常相似，在~ 1097和~ 1187 cm−1处有两个明显的波段，在798和778 cm−1处有两个微弱的波段，表明未蚀刻的古珠珠中存在莫干石和α-石英。与天然玛瑙独特的白色外观相反，蚀刻珠中的分散白色是由蚀刻反应产生的。拉曼光谱和傅里叶红外光谱均表明，蚀刻珠中不含莫干石，表明由于莫干石和部分α-石英的缺失而产生的白色散射，导致表面粗糙。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Heritage Science Arts and Humanities-Conservation

CiteScore

4.00

自引率

20.00%

发文量

183

审稿时长

19 weeks

期刊介绍： Heritage Science is an open access journal publishing original peer-reviewed research covering: Understanding of the manufacturing processes, provenances, and environmental contexts of material types, objects, and buildings, of cultural significance including their historical significance. Understanding and prediction of physico-chemical and biological degradation processes of cultural artefacts, including climate change, and predictive heritage studies. Development and application of analytical and imaging methods or equipments for non-invasive, non-destructive or portable analysis of artwork and objects of cultural significance to identify component materials, degradation products and deterioration markers. Development and application of invasive and destructive methods for understanding the provenance of objects of cultural significance. Development and critical assessment of treatment materials and methods for artwork and objects of cultural significance. Development and application of statistical methods and algorithms for data analysis to further understanding of culturally significant objects. Publication of reference and corpus datasets as supplementary information to the statistical and analytical studies above. Description of novel technologies that can assist in the understanding of cultural heritage.