绿松石结构的致密性对其颜色量化研究的影响

How Structure Compactness Impacts the Quantitative Colour Research of Turquoise

绿松石的结构致密性对其颜色量化研究工作存在重要影响。采用国际公认的色度学变量CIE 1976色差(ΔE)来表征绿松石样品在特定区域内颜色的不均一性,通过静水称重法和原子力显微镜(AFM)来表征结构致密性的体相和表相特征。结果发现,质地疏松绿松石存在较大色差、较大的表面粗糙度及较小的相对密度。激光剥蚀电感耦合等离子质谱仪(LA-ICP-MS)研究绿松石成分显示,疏松绿松石样品中致色元素含量呈现较大的测量不确定性,存在很严重的随激光剥蚀时间延长而迅速衰减的现象,而致密绿松石样品并无此现象。出土疏松绿松石样品的受沁程度和色差也明显大于致密样品。相对而言,高致密性绿松石具有相对密度较大、表面平滑度较高、颜色分布较为均一、致色元素分布较为规律、抗污染能力较强等优良特征。因此,在后续绿松石颜色量化分级工作当中,对致密性进行严格定量显得尤为必要。

The structure compactness has an important impact on the quantitative colour research of turquoise.The authors first characterized the colour heterogeneity of turquoise in certain areas by using a standard colour variable：CIE 1976 colour difference（ΔE）.The structure compactness of turquoise sample was measured by hydrostatic weighing method for bulk property and atomic force microscope（AFM）for surface property.The loose turquoise sample shows largerΔEand standard deviation,bigger roughness,and much smaller specific gravity value than that of the compacted sample.The loose turquoise sample also exhibits large uncertainties in the chemical composition.By using laser ablation inductively coupled plasma mass spectrometer（LA-ICP-MS）,the authors found that the concentrations of colour causing elements such as Cu and Fe had substantial decline along with the laser ablation time,which never happen in the compacted sample.Meanwhile,the study on unearthedancient turquoise samples shows that loose turquoise has bigger colour difference,lower anticorrosion and anti-contamination ability than that of compacted turquoise.In contrast,turquoise with compacted structure has better quality,and presents larger specific gravity,lower surface roughness,more homogeneous colour,more uniform distribution of colour causing elements,and stronger anti-contamination ability.Therefore,the authors propose that accurate description of compactness is an indispensable criterion for the further quantitative colour classification of turquoise.