Abstract
Previous studies of ancient jade using portable X-ray fluorescence (pXRF) have mostly focused on mineral identification, alteration status and provenance determination. It is usually used as an auxiliary instrument for spectroscopic detection with finer resolution. However, there is no substitute for the efficiency and stability of pXRF in-situ non-destructive analysis, which is less affected by the test environment. The scale of the data from the pXRF analysis did not allow for a more in-depth interpretation of ancient jade in the past. In this study, pXRF has been carried out for a total of 112 pieces of nephrite artifacts unearthed from the Yuehe tomb No.1 in Nanyang City, Henan Province, Central China. Certain patterns become clearer as the size of the data increases. The coefficient of variation, cluster analysis and correlation analysis can be used to separate elements into different assemblages, revealing whether the elements are from the primary and impurity minerals of nephrite itself, from the burial microenvironment in the soil, or even from other specific sources. In addition, most of the secondary whitening occurring in the batch of nephrite are accompanied by an increase in Ca content, confirming the previously refuted theory of calcification. More importantly, the principal component analysis of the twin nephrite artifacts suggests visually indistinguishable elemental changes caused by secondary changes, which may lead to misjudgment of ancient nephrite provenance using elemental data.
Highlights
Jade culture is a material culture unique to Chinese civilization, and exploring the process of the emergence and development of the civilization through jade culture has been an important area of archaeological research [1]
The coefficient of variation In probability theory and statistics, the Coefficient of Variation (CV) is used as a measure of standardized variability for each element. This was calculated by dividing the standard deviation by the mean for each element of the Yuehe nephrite data set (n = 230) (Table 1).When the CV is low, the data have less variability and higher stability
A total of 112 pieces of nephrite artifacts unearthed from the Yuehe tomb No.1 were carefully been tested by portable X-ray fluorescence (pXRF) analysis in this study and 230 data were obtained
Summary
Jade culture is a material culture unique to Chinese civilization, and exploring the process of the emergence and development of the civilization through jade culture has been an important area of archaeological research [1]. The composition of nephrite is close to the monomineralic represented by the minerals of isomorphic tremolite-ferroactinolite series, so it can be composed either of iron-rich (actinolite) or magnesium-rich (tremolite) varieties with average chemical formula C a2(Mg,Fe)5[Si8O22] (OH)2 [7]. The dependence of the contents of the basic formula and impurity elements in nephrite elemental composition has been the subject of a number of studies in recent decades [9]. With this trend, plenty of past studies focused on the elemental analysis of antique nephrite were mainly for the purpose of providing information for relics conservation and for tracking or discriminating the provenance [5, 11, 12]. X-ray fluorescence (XRF) spectrometry and some innovative techniques such as PIXE are most popular [13,14,15]
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