还原法热处理锆石的宝石学特征及颜色初探

剡晓旭; 岳素伟; 李穗钿; 王沛炼

doi:10.15964/j.cnki.027jgg.2021.04.005

还原法热处理锆石的宝石学特征及颜色初探

剡晓旭^{1, 2},
岳素伟^{1, 2, ,},
李穗钿¹,
王沛炼^{1, 2}

1.
广州城市理工学院珠宝学院, 广东广州 510800
2.
广州城市理工学院珠宝研究所, 广东广州 510800

基金项目:

广东省教育厅特色科研类项目 CQ180002

广州城市理工学院优博项目 YB1700001

详细信息

作者简介:
剡晓旭(1988-)，男，讲师，主要从事宝石鉴定工作

通讯作者:
岳素伟(1985-)，男，副教授，主要从事宝石鉴定及矿床学的教学和科研工作。E-mail: doctor-yue@foxmail.com

中图分类号: TS93
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出版历程
- 收稿日期: 2020-12-15
- 刊出日期: 2021-06-30

Gemmological Characteristic and Colour of Zircon under Heat Treatment in Reducing Condition

YAN Xiaoxu^{1, 2},
YUE Suwei^{1, 2, ,},
LI Suitian¹,
WANG Peilian^{1, 2}

1.
School of Jewelry, Guangzhou City University of Technology, Guangzhou 510800, China
2.
Institute of Jewelry, Guangzhou City University of Technology, Guangzhou 510800, China

摘要

摘要: 热处理可以去除锆石中因放射性衰变而产生的色心，从而改善其颜色和透明度，提升其观赏价值和商业价值。市场上，绝大多数的蓝色锆石为红褐色锆石经高温热处理获得，其颜色成因目前一直存在争议。笔者选取红褐色锆石和黄褐色锆石样品，通过高温还原法热处理，探索其颜色变为蓝色的最佳温度，同时结合常规宝石学测试、红外光谱和紫外-可见吸收光谱测试，分析其热处理前、后的特征变化。结果显示，还原条件下，950~1 000 ℃的热处理实验可以使红褐色锆石变为浅蓝色。红外光谱测试结果显示，热处理前锆石样品434 cm^-1和610 cm^-1指示其非晶质化程度不高；热处理后，438/436 cm^-1吸收增强，1 100~900 cm^-1吸收变窄，说明热处理使锆石的结晶程度略有增强。紫外-可见光谱测试结果显示，热处理前位于510 nm附近的宽吸收带由Y³⁺替换Zr⁴⁺所致，是锆石样品呈现红褐色的原因；热处理后，Y³⁺产生的色心分解致使510 nm处吸收消失，而800 nm处吸收峰大大减弱，相伴出现640 nm附近的宽吸收，653 nm和690 nm处的较强吸收峰和一系列弱吸收峰由U⁴⁺ (U⁵⁺+e^-→U⁴⁺)所致；可见光范围内出现640 nm处宽吸收带是锆石呈蓝色的主要原因，可能是653 nm强吸收与附近一系列弱吸收峰的整体表现。
- 锆石 /
- 热处理 /
- 还原法 /
- 宝石学特征 /
- 颜色成因
Abstract: The colour center caused by radioactive decay in zircons can be removed by heat treatment. This behavior also may modify their colour and transparency to improve the ornamental and commercial value. A large majority of blue zircons in the market are obtained from reddish-brown zircon by heat treatment under high temperature. However, the colour mechanism of which have long been controversial.Reddish-brown and yellowish-brown zircons were applied in this study, and heated in reducing atmosphere in order to confirm the optimum temperature of blue colour modification. The mechanism of altering colour in heat treatment was also investigated in this study by analyzing their standard gemmological properties, infrared absorption spectroscopy (IR) and ultraviolet-visible spectrophotometry (UV-Vis). The results of heat treatment showed that reddish-brown zircons could be changed into light blue zircons by heat treatment under 950-1 000 ℃ in reducing atmosphere.The IR spectra of the samples at 434 cm^-1 and 610 cm^-1 before heat treatment show their low metamictization.After heat treatment, the absorption of 438/436 cm^-1 (peak) get strengthened and the 1 100-900 cm^-1 (band) narrowed down, which indicates that the crystalline state of the samples restored. The UV-Vis spectra of the samples showed that the absorption band around 510 nm was generated by Y³⁺substituting with Zr⁴⁺, leading to radiation and turned colourless crystalline zircons into reddish-brown metamict ones. After heat treatment, the vanishment of 510 nm band was caused by the breaking down of colour center generated by Y³⁺substitution. The 800 nm band showed weak intensity, with the emergence of absorption around 640 nm. The strong absorption peak of 653 nm and 690 nm and a series of weak absorption peaks were caused by U⁴⁺. The 640 nm band was presumed to be the main cause of the blue colour of the treated samples, and the 653 nm with its surrounding absorptions might relevant to it.
- zircon /
- heat treatment /
- reduction method /
- gemmological characteristic /
- colour mechanism

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图 1 内蒙古角力格泰地区碧玺样品

Figure 1. Tourmaline samples from Jiaoligetai area, Inner Mongolia

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图 1 热处理前后锆石样品的外观特征

注：小图中左侧为热处理前，右侧为热处理后

Figure 1. Appearance characteristics of zircon samples before and after heat treatment in reducing condition

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图 2 热处理前、后锆石样品Zir-05(a)和Zir-08(b)的红外吸收光谱

Figure 2. IR spectra of zircon sample Zir-05(a) and Zir-08(b) before and after heat treatment

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图 3 热处理前、后的锆石样品Zir-05(a)和Zir-08(b)紫外-可见光吸收光谱

Figure 3. UV-Vis spectra of zircon sample Zir-05(a) and Zir-08(b) before and after heat treatment

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表 1 锆石样品的热处理实验方案

Table 1 The heat treatment schemes of zircon samples

实验方案	目标温度/℃	加热速率/℃·min^-1	恒温时间/h	热处理样品号
实验一	900	4	2	Zir-01，Zir-02
实验二	950	3	2	Zir-03，Zir-04
实验三	950	4	2	Zir-05，Zir-06
实验四	1 000	4	2	Zir-07，Zir-08

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参考文献(16)

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