| Summary: | 博士 === 國立成功大學 === 資源工程學系 === 102 === Non-destructive Testing Analysis the Ancient Glass Beads
Unearthed from the Chungde Site, Hualien
Shih-Chung Wang
Yun-Hwei Shen
Department of Resources Engineering ＆ College of Engineering
SUMMARY
The ancient glass beads with variant colors, shapes, and stylistics possess socio-cultural significance, and have been an important approach to understand the topics for the origin and provenance, manufacturing techniques, and exchange/trade routes.The chemical composition of ancient glass beads as the source area, place of production workshop, add material changes with the times, glass bead color and chemical composition, and may be affected by factors, including raw materials, fluxing agents, colorants, opacifiers and stabilizers.
Because artifacts have the preciousness and rarity, using non-destructive detection method for artifacts become more important, along with scientific instruments in non-destructive testing technology in more significant progress. In this research, micro-Raman spectroscopy and micro X-ray fluorescent spectrometer (μ-XRF) are used in combination to examine ten ancient glass beads excavated from Chungde site, Hualien, Taiwan, dated back to 1500-800BP, to unravel the mineralogical and chemical compositions. From micro Raman spectrometer analysis results displaying the most of Chungde site glass beads are glass and anorthite glass, analysis and calculation specimens of Raman spectrogram, the results of Ip (the Raman Index of Polymerization) indicate that the sintering temperature is about 1000~1400°C rather than the ancient alkaline glass range, which is about 800 ~1000°C, because the ancient glass beads are classified high aluminum of soda-lime glass system.
Micro X-ray fluorescence spectrometer (μ-XRF) for ancient glass beads of chemical composition analysis, generally get the kind of ancient glass beads ingredient may use additives which like fluxing agents: Na, K; stabilizers: Ca, Mg; colorants: Fe2+, Cu+, Cu2+; opacifiers: none. The chemical composition of samples, Na2O, K2O, CaO, MgO and Al2O3, were analyzed by a ternary phase diagram , respectively with CaO - (MgO + K2O) - Na2O, K2O - Al2O3 - CaO, CaO - K2O - Na2O phase diagrams which were used for classification of ancient glass beads. According CaO - K2O - Na2O and K2O - Al2O3 - CaO of phase diagrams displayed, the research of glass beads mostly are high aluminum soda-lime-silicate system, which belong to Indo - Pacific glass beads, but the only two of samples are low aluminum soda-lime-silicate system. These low aluminum soda-lime-silicate system glass beads, according to their era, and geographical distribution and archaeological site of data displayed, are mostly like glass beads which are manufactured from Taiwan.
Key words: Micro-Raman Spectroscopy, Micro-XRF Spectrometer, the Raman Index of Polymerization, Indo-Pacific Beads
INTRODUCTION
Ancient glass beads are small in size and easy to carry, rounded appearance, bright luster, rich colors and can be arranged through a combination of changes in style and used as ornaments, ritual items, funerary purposes, and glass beads in different shapes and colors, can be used as a social class, a symbol of wealth, sex and other social and cultural significance. The chemical composition of ancient glass beads as the source area, place of production workshop, add material changes with the times, glass bead color and chemical composition, and may be affected by factors, including raw materials, fluxing agents, colorants, opacifiers and stabilizers.
MATERIALS AND METHODS
Due to prehistoric heritage has precious and rare characteristics, so this research using micro Raman spectroscopy, and micro X-ray fluorescent spectrometer (μ-XRF) on Hualien County Chongde site unearthed of 10 pieces ancient glass beads for analysis.
RESULTS AND DISCUSSION
The 10 pieces specimens analysis of results finishing into table 1, spectrum identification proceeds of mineral to glass, and anorthite glass mainly, other is has: quartz, albite, dolomite, ankerite and amazonite, chemical components analysis of results displayed, roughly can will 8 pieces glass beads presumption soda-lime-silicate system, TP1-004 may for a lkali-silicate system, with the exception of TP1-054 and TP2-002, the remaining samples without lead and alumina (Al2O3) content is high, presumably for India-Pacific glass beads, TP1-038 is possible for soda-lead-silicate system but it can have a higher alumina content, also belong to India-Pacific glass beads.
Making glass by fluxing agents are Na and K ( TP1-038 for Na, K and Pb ), stabilizers to Ca mainly, only 6 pieces have another contains Mg, and without any opacifiers , part of ancient glass beads with orange color, according to its chemical elements analysis most contains Cu, speculated that colorants are from cuprite (Cu2O) like copper ion (Cu+), but Raman spectrum does not display spectrum diagram of this mineral, speculated that Cu+ may be totally dissolving in glaze, that cannot be detected by Raman spectrometer, TP1-051’s color is blue-green and colorant is Cu2+, and it is different from the colorants are used by Cu+, TP-054 and TP2-002 for long tube blue glass beads, speculated that their colorants are Fe2+.
Table1. The result of Raman spectrum and μ-XRF chemical composition
NO. MINERAL COMPOSITION GLASS SYSTEM FLUXING AGENTS STABILIZERS COLORANTS
TP1-003 glass、anorthite glass Soda-lime systems Na, K Ca Cu+
TP1-004 glass、anorthite glass、quartz, ankerite Alkali-silicate system Na, K Ca, Mg Unknown
TP1-017 glass、anorthite glass、quartz Soda-lime systems Na, K Ca, Mg Cu+
TP1-024 glass、anorthite glass Soda-lime systems Na, K Ca Cu+
TP1-036 glass、anorthite glass、quartz, zircon, amazonite Soda-lime systems Na, K Ca, Mg Cu+
TP1-037 glass、anorthite glass、quartz、albite、dolomite Soda-lime systems Na, K Ca, Mg Cu+
TP1-038 glass、anorthite glass、quartz、albite、dolomite Soda-lead-silicate system Na, K, Pb Ca Cu+
TP1-051 glass、anorthite glass Soda-lime systems Na, K Ca Cu2+
TP1-054 glass Soda-lime systems Na, K Ca, Mg Fe2+
TP2-002 glass Soda-lime systems Na, K Ca, Mg Fe2+
From micro Raman spectroscopy analysis results displayed Chongde glass beads of mineral components composition more for glass and anorthite glass, also, analysis and calculation specimens of Raman spectrogram by get of the Raman index of polymerization (Ip). To display their sintering temperature of about 1000~1400℃, not the traditional alkaline glass systems 800~1000℃, may the effects of soda-lime glass systems containing alumina.
The result of specimens in the of chemical components: using Na2O, K2O, CaO, MgO and Al2O3 as end member which were analyzed by ternary phase diagram, respectively to CaO – (MgO+K2O) – Na2O,K2O – Al2O3 – CaO, CaO – K2O – Na2O phase diagrams which were used for classification of ancient glass beads. According to CaO – K2O – Na2O and K2O – Al2O3 – CaO of phase diagram displayed, this research of glass beads main for high aluminum soda-lime glass system, the inference that belongs to India-Pacific glass beads, but one of two glass beads for low-aluminum soda-lime glass systems.
CONCLUSION
Due to archaeological finds of rare and precious, non-destructive testing analysis on unearthed of analysis work increasingly important, this for Hualien Chongde site ancient glass beads, used non-destructive testing analysis method, on its mineral, and chemical composition of detection, and according to its characteristics analysis and discussion, determines ancient glass belongs to what glass system, how can for its making technology, and trade way and culture exchange will be in the future discussion.
(1) This research application Raman spectroscopy on ancient glass beads of non-destructive analysis, get Chongde glass beads of mineral components composition more for glass and anorthite glass, but other additives (as fluxing agents, and colorants, and opacifiers) of components and species does not in this research which has obviously of spectrum pattern, that may in sintering process has completely of dissolving in glaze or glass that cannot be detected.
(2) From micro Raman spectroscopy analysis results displayed Chongde glass beads of mineral components composition more for glass and anorthite glass, also, analysis and calculation specimens of Raman spectrogram by get of the Raman index of polymerization (Ip). To display their sintering temperature of about 1000~1400℃, not the traditional alkaline glass systems 800~1000℃, may the effects of soda-lime glass systems containing alumina.
(3) Using Ip, ν-max Si-O stretching peak wave number and δ-max Si-O bending peak wave number are compared with predecessors research in the chemical composition and data of Raman spectrum, cannot be fitted, main due to is in India-Pacific glass beads of Raman spectrum data of insufficient, and part data is with porcelain of data to instead of.
(4) Micro X-ray fluorescence spectrometer (μ-XRF) constituent analysis of ancient glass beads, which been additive components of ancient glass beads may be used fluxing agents: Na2O, K2O; stabilizers: CaO, MgO; colorant: Fe2+, Cu+ and Cu2+; without opacifiers.
(5) The result of specimens in the of chemical components: using Na2O, K2O, CaO, MgO and Al2O3 as end member which were analyzed by ternary phase diagram, respectively to CaO – (MgO+K2O) – Na2O,K2O – Al2O3 – CaO, CaO – K2O – Na2O phase diagrams which were used for classification of ancient glass beads., the research of glass beads mostly are high aluminum soda-lime-silicate system, which belong to Indo - Pacific glass beads, but the only two samples are low aluminum soda-lime-silicate system. These low aluminum soda-lime-silicate system glass beads, according to their era, and geographical distribution and archaeological site of data displayed, are mostly like glass beads which are manufactured from Taiwan.
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