方沸石作为一种工业常见矿物, 在工业中被广泛应用, 方沸石的合成方法也极其成熟, 但可以用作宝石的天然方沸石却在世界范围内都非常少见。 该文讨论对象为湖北大冶矿区产出的天然宝石级方沸石, 旨在为对其进行种类鉴别并阐述其产地特征与鉴定依据。 该产地的方沸石多呈无色透明, 晶型完整者多见, 晶面花纹清晰, 晶体粒径最大可达36 mm, 总体净度较好。 通过背散射电子观察结果确定样品成分均匀, 结合XRD谱图及能谱分析结果计算确定该晶体为方沸石; 内部可见白色包裹体, 具束状结构与一组解理, 电子探针结果计算判断内部包裹体为交代残余结构的的斜钙沸石。 拉曼光谱特征如下: 81、 139、 201和298 cm-1的峰是由沸石的晶格振动导致; 298 cm-1的强峰可能代表金属氧的振动; 491 cm-1的极强峰是由O-Si-O键的弯曲振动导致的; 390、 671 cm-1的峰可能归因于硅氧和铝氧四面体的移位; 1 105 cm-1的一组峰指示硅氧四面体的伸缩振动, 这是天然沸石的典型峰位。 1 624 cm-1的弱峰则代表水的弯曲振动, 3 557 cm-1的强峰代表水的伸缩振动。 样品红外光谱主要表现为: 红外吸收谱线788、 1 259 cm-1是由硅氧四面体的伸缩振动导致的。 1 646 cm-1是由水的弯曲振动导致的; 3 635 cm-1弱吸收是由水的伸缩振动导致的。 部分样品仅可见3 635 cm-1一处吸收, 表明其内部水分子仅以一种形式参与晶格, 可见溶蚀凹坑与绿泥石的样品除3 635 cm-1一处吸收外, 在其左侧均可见吸收但3 635 cm-1强度相对较高, 表明其结构内水分子以多种形式参加晶格且数量稍多, 但总体仍较少。 结合光谱、 成分测试推测湖北大冶宝石级方沸石为高温沉积型方沸石, 交代斜钙沸石成矿, 后期经历了局部绿泥石化。

As a common mineral, analcime has been widely applying in industry. The compound methodsof analcimearealso mature, but the natural gem-gradeanalcimeis still very rare on Earth. In this paper, the object of discussion is the natural gem-gradeanalcime from the Daye mining area of Hubei province. The purpose is providing its identification and characteristics of origin. These analcimein this area are mostly colorless and transparent, with complete crystal shape and clear crystal surface pattern. The maximum crystal size can reach 36 mm; of course, the clarity of these is excellent too. According to the backscattered electron imagingand energy spectrum analysisresults, determined the crystal is homogeneous analcime. The white inclusion is wairakites with fascicular structure, a set of cleavage and metasomatic relict texture according to the electronic probe microanalyzer results calculation. The characteristics of Raman spectra show that: the diffraction peaks of 81, 139, 201 and 298 cm-1 are caused by the lattice vibration of zeolite. The strong peak of 298 cm-1 may represent the vibration of metal-oxygen. The bending vibration of O-Si-O causes the extremely strong peak of 491 cm-1. The shift of Si-O and AlO tetrahedrons may attribute the diffraction peak of 390, 671 cm-1. A set of peaks at 1 105 cm-1 indicates the stretching vibration of Si-O, which is a typical peak position of natural zeolite. The weak peak of 1 624 cm-1 represents the bending vibration of water, and the strong peak of 3 557 cm-1 represents the stretching vibration of water. The samples infrared spectra mainly show that: the infrared absorption 788, 1 259 cm-1 are caused by the stretching vibration of silica tetrahedron. The bending vibration of water causes 1 646 cm-1; The weak absorption of 3 635 cm-1 is caused by the tensile vibration of water. For some complete samples, only one absorption can be seen at 3 635 cm-1, which means there is only one form of water molecule in the lattice. In other samples with pocket and chlorite, the 3 635 cm-1 absorptions can be seen on the left side between 3 635 cm-1 with strong absorption, which means the type of water molecules in the lattice are various, and the number is slightly larger than the rest, but still fewer overall. Therefore, according to the composition and spectrumtest, it is speculated that the gem-grade calcite in Hubei Daye belongs to high-temperature sedimentary analcime, which are the metasomatic products of wairakites, and later experienced local chloritization.