Analysis on Chemical Composition and Heat Treatment Result of Light Yellow Scapolite
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摘要: 方柱石是自然界中一种比较常见的矿物，颜色丰富、透明度高、颗粒较大者被应用于宝石领域。本文对来自非洲某地的12颗浅黄色方柱石样品进行常规的宝石学测试，并随机选择3颗方柱石样品利用LA-ICP-MS测试其化学成分，通过阴离子法数据分析和计算的结果表明，3颗方柱石样品均为方柱石族中的针柱石。为了确定恒温温度、恒温时间、热处理气氛三个主要因素对方柱石颜色的影响，设计了不同参数的热处理实验，在实验过程中添加活性炭营造还原气氛，对比热处理前、后方柱石样品的紫外-可见光光谱变化特点，利用色纯度降低率公式分析颜色改变的效率。实验结果说明，在恒温温度为600℃和恒温时间6 h的热处理条件下，方柱石样品的天然色心能被有效消除，颜色由原来的浅黄色转变为无色，色纯度降低率最高可达64.57%，且改色效果理想稳定。Abstract: The scapolites are relatively common minerals in nature. Those ones with rich colour, high transparency and larger sizes are used in gems. In this paper, 12 pieces of light yellow scapolite samples from Africa were tested by conventional gemmological methods, and 3 pieces of scapolite samples were selected randomly for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for chemical composition. Utilizing anion analysis, the LA-ICP-MS data showed that this batch of samples were dipyres in the scapolite group. Moreover, in order to determine the effect of heating temperature, holding time and atmosphere on its colour and to obtain the most effective treatment parameters, different heating processes were designed. During the heating process, the authors added activated carbon powder to create a reducing atmosphere. UV-Vis spectra were obtained and compared before and after heat treatment. The formula of fading colour was used to analyze the efficiency of colour change so that the best conditions for heat treatment of scapolites can be determined. Consequently, to summarize, heating to 600℃ and keeping for 6 hours, the colour of scapolite samples could fade dramatically from light yellow to colourlessness, and the reduce rate of colour purity was 64.57%.
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Keywords:
- scapolite /
- heat treatment /
- chemical composition /
- experimental parameter
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