绿松石与磷铝石的宝石学特征对比研究

Comparative Study on Gemmological Characteristics of Turquoise and Variscite

绿松石和磷铝石外观上相似,且产地众多,本文选取3颗湖北竹山绿松石、4颗安徽马鞍山绿松石、3颗美国犹他州磷铝石和3颗安徽马鞍山磷铝石共计13颗样品作为研究对象,进行常规宝石学测试和红外光谱、紫外光谱、X射线荧光能谱等测试,对绿松石和磷铝石的常规宝石学特征和谱学特征进行对比、总结和归纳。绿松石与磷铝石的相对密度近似,红外光谱测试绿松石和磷铝石区别主要体现在3600~3400 cm^(-1)范围内,绿松石有两个结构水的吸收峰,而磷铝石只有一个结构水吸收峰;1200~1000 cm^(-1)范围内,绿松石具有四个与PO_(4)^(3-)伸缩振动有关的吸收峰,而磷铝石只有两个,且绿松石的主吸收峰为1119 cm^(-1)处,磷铝石的主吸收峰在1056 cm^(-1)处。竹山和马鞍山绿松石紫外可见光谱出现由Fe^(3+)的^(6)A_(1)→^(4)E_(g)+^(4)A_(1)(4G)跃迁所致的427 nm处吸收和由Cu^(2+)的^(2)E_(g)→_(2)T_(2g)跃迁所致665 nm后的平直吸收带;美国犹他州和安徽马鞍山磷铝石紫外可见光谱主要存在由V^(3+)的^(3)T_(1g)(F)→^(3)T_(2g)(F)跃迁与Fe^(3+)的^(6)A_(1g)→^(4)T_(2g)跃迁联合所致的639 nm处吸收峰,结合XRF测试结果,绿松石的颜色与Cu和Fe有关,磷铝石的颜色主要与Fe和V有关。

Turquoise and variscite are similar in appearance and have many origins.This paper selects 13 samples,including 3 turquoise from Zhushan,Hubei Province,4 turquoise from Ma'anshan,Anhui Province,3 phosphorite from Utah,United States,and 3 phosphorite from Ma'anshan,Anhui Province,as research objects,and conducts conventional gemmological tests,infrared spectra,ultraviolet spectra,X-ray fluorescence spectra and other tests to compare and summarize the conventional gemmological characteristics and spectral characteristics of turquoise and variscite.The specific gravity of turquoise is similar to that of variscite.The difference between turquoise and variscite is mainly reflected in the range of 3600~3400 cm^(-1)measured by infrared spectrum.turquoise has two absorption peaks of structural water,while variscite has only one absorption peak of structural water;In the range of 1200~1000 cm^(-1),turquoise has four absorption peaks related to PO_(4)^(3-)stretching vibration,while there are only two for variscite,and the main absorption peak of turquoise is 1119 cm^(-1),and the main absorption peak of variscite is 1056 cm^(-1).The UV visible spectra of Zhushan and Ma'anshan turquoise show a flat absorption band at 427 nm caused by the^(6)A_(1)→^(4)E_(g)+^(4)A_(1)(4G)transition of Fe^(3+)and 665 nm caused by the^(2)E_(g)→^(2)T_(2g)transition of Cu^(2+);The UV-VIS spectra of variscite from Utah and Maanshan,Anhui,mainly show an absorption peak at 639 nm caused by the^(3)T_(1g)(F)→^(3)T_(2g)(F)transition of V^(3+)and the^(6)A_(1g)→^(4)T_(2g)transition of Fe^(3+).Combined with the XRF test results,the color of turquoise is related to Cu and Fe,and the color of variscite is related to Fe and V.At the same time,the infrared and ultraviolet spectral characteristics provide a certain basis for distinguishing the origin of turquoise and variscite.