危地马拉翡翠宝石矿物学特征及其与缅甸翡翠的对比研究

Characteristics of the Guatemalan Feicui and Its Comparison to the Myanmar Feicui

危地马拉目前已成为仅次于缅甸的第二大翡翠原料供应地。这两个产地翡翠辨别的需求愈发迫切,且应用意义较大。采用显微镜观察、电子探针分析及背散射电子照相获得危地马拉蓝水料翡翠的矿物成分及结构构造特征,结合两产地翡翠产出的大地构造环境、自然地理环境、原石特征与矿物成分特征等进行对比分析。总体上,危地马拉翡翠次生原石有一定的磨圆,呈次棱角状,"皮"(风化皮)厚度较薄,较少出现翻砂现象,由"皮"向里,极少甚至几乎不存在"红雾"。相对地,缅甸翡翠次生原石发育显著的球状风化,原石通常有较好的磨圆度,棱角状不明显,"皮"厚度可达数厘米,用手压磨有显著的翻砂现象,"皮""肉"之间偶可见"红雾"。硬玉与绿辉石成分判别图显示危地马拉翡翠中硬玉和绿辉石呈相对富Ca、贫Na的特征,而缅甸翡翠中硬玉和绿辉石整体呈相对贫Ca、富Na的特征。在Fe含量上,危地马拉翡翠中硬玉的Fe含量较缅甸翡翠中硬玉的Fe含量偏低,而危地马拉翡翠中绿辉石的Fe含量较缅甸翡翠中绿辉石的Fe含量偏高。对翡翠外观特征的充分对比和对判别图的综合分析可应用于实际中翡翠产地的区分。

Guatemala is the second largest producing area of feicui after Myanmar. The demand for the identification of feicui from the two origin areas is becoming more and more urgent, which is of great significance. The mineral composition, texture and structure characteristics of Guatemalan blue water jade were obtained by microscope observation, electron microprobe test and back-scattered electron images(BSE). Combined with the data of the tectonic environment, natural geographical environment, rough stone characteristics, and mineral composition characteristics of feicui from the two producing areas, a comparative analysis was made. The results show that compared with Myanmar jade, the weathered crust of the Guatemalan feicui is less rounded but thinner, with less granular tactile sensation, and little or almost no “red fog” from the skin inward. On the other hand, there are significant spherical weathering characters in the rough stones of Myanmar, the weathering crust is usually well rounded, thicker, and gritty to the touch. “Red fog” can be occasionally seen between the weathering crust and jade of the Myanmar feicui. The discriminant diagram of jadeite and omphacite composition shows the jadeite and omphacite from Guatemala appear relatively rich in Ca, and poor in Na, while the jadeite and omphacite from Myanmar are relatively poor in Ca, rich in Na. In terms of Fe content, the jadeite in the Guatemalan feicui is lower than that in the Myanmar feicui, while the omphacite in the Guatemalan feicui is higher than that in the Myanmar feicui. It can be used to distinguish the origin of feicui in actual production by comparing the appearance characteristics of feicui fully and analyzing the discriminant map comprehensively.