Dark blue lazurite from the Malo-Bystrinskoe lazurite deposit, Baikal Lake area, Eastern Siberian region, Russia, was analyzed by electron microprobe and revealed an unusually high content of total sulfur corresponding to 8.3 wt% S. The relative content of sulfur in sulfate and sulfur in sulfide form was determined by wet chemical analysis. The H2O content was measured by means of differential thermal analysis in combination with mass spectrometry and infrared (IR) spectroscopy. The charge-balanced empirical formula of lazurite calculated on the basis of 12 (Al+Si) atoms per formula unit was (Na6.97Ca0.88K0.10)Σ7.96[(Al5.96Si6.04)Σ12O24](SO4)1.092−(S3−)0.55S0.052− Cl0.04·0.72H2O. The presence of H2O molecules and (S3)– and (SO4)2– groups was confirmed by the combination of IR, Raman, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) methods. The idealized formula of lazurite is Na7Ca[Al6Si6O24](SO4)2–(S3)–·H2O, and it is believed that extra-framework cations and anions are grouped into clusters of [Na3Ca·SO4]3+ and [Na4(S3)–]3+. The types of isomorphous substitutions in nosean and haüyne are discussed. Lazurite is a clathrate-type mineral, which may be an effective (S3)– sensor due to the stability of the trisulfur radical anion in isolated cages of the crystal structure. This specific feature makes it possible to study the behavior of this ubiquitous radical anion over larger T and P ranges as compared to free species. This kind of lazurite, with oxidized and reduced sulfur species, seems to be appropriate for the estimation of the fugacity of SO2 and O2 in metasomatic systems forming lazurite-containing rocks. The systematic presence of incommensurate modulations is a unique structural feature of Baikal lazurite and may be an important marker indicating provenance of the mineral.

中文翻译：

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关于富硫天青石的晶体化学，理想的是Na7Ca（Al6Si6O24）（SO4）（S3）–·nH2O

用电子探针分析了俄罗斯西伯利亚东部贝加尔湖地区Malo-Bystrinskoe天青石矿床中的深蓝色天青石，并通过电子探针对其进行了分析，结果发现总硫的含量异常高，相当于S的8.3 wt％。通过湿化学分析确定硫化物形式的硫。通过差示热分析结合质谱和红外（IR）光谱法测量H2O含量。基于每个公式单元12个（Al + Si）原子计算的天青石的电荷平衡经验公式为（Na6.97Ca0.88K0.10）Σ7.96[（Al5.96Si6.04）Σ12O24]（SO4）1.092 -（S3-）0.55S0.052-Cl0.04·0.72H2O。IR，拉曼光谱，电子顺磁共振（EPR）结合证实了H2O分子以及（S3）–和（SO4）2–基团的存在，和X射线光电子能谱（XPS）方法。天青石的理想分子式为Na7Ca [Al6Si6O24]（SO4）2–（S3）–·H2O，据信骨架外阳离子和阴离子分为[Na3Ca·SO4] 3+和[Na4（S3） ）–] 3+。讨论了鼻和哈伊恩中同构取代的类型。Lazurite是一种包合物型矿物，由于三硫自由基阴离子在晶体结构的隔离笼中的稳定性，因此可能是一种有效的（S3）–传感器。与自由物种相比，这种特殊的特征使得有可能研究这种普遍存在的自由基阴离子在更大的T和P范围内的行为。这种具有氧化和还原的硫物种的天青石似乎适合估算形成含有天青石的岩石的交代体系中SO2和O2的逸度。