石英质玉石的“起棉”现象及其成因机理

“Whitening Phenomenon”of Quartzite Jade

  • 摘要: 国内珠宝市场上的部分石英质玉石在放置一段时间后会出现“起棉”现象,主要表现为玉石外观泛白、透明度降低,现有文献对此并未给出科学解释。通过浸水实验,对比实验过程中“起棉”样品与不“起棉”样品在外观特征、内部微细结构、光谱特征等方面的变化,并结合浸油和浸蜡实验,探讨“起棉”现象产生的原因。实验结果表明,日常条件下的“起棉”现象具有可恢复性,“棉”的产生主要原因是由于玉石中的吸附水或后期人工加入的油/蜡等充填物流失,使宽度为几百纳米的微裂隙或颗粒间隙逐渐显现,光线在其中传播时发生散射。石英质玉石质地越疏松,玉石越易“起棉”。

     

    Abstract: In domestic jewelry market,some quartzite jade displays the"whitening phenomenon"with the appearance whitening and the transparency reducing.However,it is unclear in possible formation mechanism.In this article,the variations of apparent characteristics,internal texture and spectral signature were compared for the samples before and after the"whitening phenomenon".It was found that the"whitening phenomenon"occurred under daily condition was recoverable.Its emergence is mainly due to the loss of fillings,such as absorbed water,silicon oil and liquid paraffin,which can make the several-nanometer-wide micro fractures or large grain boundaries gradually emerge and cause light scattering.The"whitening phenomenon"could be more easily observed in the quartzite jade with loose structure and larger grain size.

     

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