X-ray粉末繞射與拉曼光譜在古玉器鑑定原理與範例之探討

A Study on Principles and Case Study of Identifying Materials of Ancient Jade Artifacts by Raman Spectrum and X-Ray Diffraction

利用有糸統的科學分析方法，進行市售10件古玉器材質分析及成分鑑定。首先採用歸納和類比相結合，由於古玉器形是一個奧秘，故結合紋飾及器形的方式，分析各個歷史朝代古玉器的總體特徵，包括玉器的品種、玉質、形制、雕工、紋飾和工藝等特徵，提供初步鑑別。選出十種購自台北玉市，供研究之古器物，以阿基米德原理測定比重值，最後使用珠寶玉石高階鑑定儀器，拉曼光譜及X光粉末繞射分析法(XRD)進行測定及礦石化學組成份之分析。結果顯示：以阿基米德原理測定比重後，將樣品分為兩類，樣品2（飾龍胎圭）、4（龍形袖飾舞人）、6（胖C型龍）、7（瘦C型龍）、8（岩璧）、9（雙象形器）及10（龍首圭）比重值高於2.9；樣品1（古蟬）、3（雕龍佩飾）、5（龍鈕印）屬於比重值低於2.9。屬於比重值低於2.9的3個樣品，經X-ray繞射與拉曼光譜分析，結果：樣品1為白雲石、樣品3及5為蛇紋石；樣品2、4、6、7、8、9及10比重值高於2.9，X-ray繞射與拉曼光譜結果，顯示均為閃玉。本次初步進行X-ray粉末繞射與拉曼光譜在古玉器鑑定原理與範例之探討，顯示具有重大意義。

Through systematic and scientific method, we have identified the materials and compositions of ten exemplary ancient jade artifacts on sales on the commercial jade market. Since the shape and iconography of ancient jade artifacts represent a form of mystery, we first resorted to the induction and analogy of decor patterns and geometric shapes as well as iconography of the jade artifacts to analyze the general features representative of each past period or dynasty in the Chinese history, including the jade material (composition), quality, iconography, carving style, decor, and artware. Through initial filtering, we carefully chose ten ancient jade artifacts from local Jade Market as samples for our investigation. Next, we determined their specific gravity by the Archimedes principle, followed by the analysis through jewel-grade analyzing equipment, Raman spectrum, and x-Ray Diffraction (XRD) to identify the chemical composition of the minerals. Our results show that samples can be categorized into two groups by their specific gravity. The first group consists of seven samples with specific gravity greater than 2.9, namely, Sample #2 (gui with pig dragon decor), Sample #4 (dancer with long sleeves), Sample # 6 (fat C-dragon), Sample #7 (slender C-dragon), Sample #8 (rock carving showing hunting by stone age people), Sample # 9 (ornament with dual elephant), and Sample #10 (dragon-headed gui). While the second group is composed of the remaining three samples with specific gravity smaller than 2.9, namely, Sample #1 (archaic cicada), Sample #3 (pendant with dragon decor), and Sample #5 (seal with dragon decor). X-ray diffraction and Raman spectrum both confirm that the materials for the three samples in the second group are dolomite for Sample #1, serpentine for Samples #3 & 5. While for all the samples in the first group with specific gravity greater than 2.9, they all belong to nephrite.