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Abstract <p>The crystal structure of a low-calcium representative of the eudialyte group from Lovozero (Kola&#xa0;Peninsula) was studied by single-crystal X-ray structural analysis in the framework of the <i>P</i>3 group, 165&#xa0;positions, <i>R</i> = 5.4%, 4469 reflections with <i>F</i> &gt; 2σ(<i>F</i>). The mineral with the idealized formula Na<sub>15</sub>(Ca<sub>3</sub>Mn<sub>3</sub>)Zr<sub>3</sub>(Fe,Zr)<sub>3</sub>(Si,Ti)(Si,Nb)[Si<sub>3</sub>O<sub>9</sub>]<sub>2</sub>[Si<sub>9</sub>O<sub>27</sub>]<sub>2</sub>O<sub>2</sub>(OH,F,Cl)<sub>2</sub>·2H<sub>2</sub>O is a Sr-containing analogue of oneillite with a low niobium content and a predominance of silicon both in the <i>M</i>3 and <i>M</i>4 positions. The&#xa0;unit-cell parameters are <i>a</i> = 14.192(2) Å, <i>c</i> = 30.170(5) Å, <i>V</i> = 5262.74 Å<sup>3</sup>. Within the <i>P</i>3 model, in addition to the oneillite-type ring [Ca–Mn], the eudialyte ring [Ca–Ca] and the ring of the composition [Na–(Ca,Sr)] are also established. The crystallochemical role of strontium in minerals of the eudialyte group is analyzed.</p>

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Dissymmetrization in Eudialyte-Group Minerals: VII. Role of Strontium in the Framework of the P3 Structure Model of High-Silicon Oneillite Analogue from Lovosero Massif

  • 期刊论文

  • 发表日期：

    2026年2月1日

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  • R. K. Rastsvetaeva,
  • V. M. Gridchina,
  • N. V. Chukanov,
  • S. M. Aksenov

摘要

Abstract

The crystal structure of a low-calcium representative of the eudialyte group from Lovozero (Kola Peninsula) was studied by single-crystal X-ray structural analysis in the framework of the P3 group, 165 positions, R = 5.4%, 4469 reflections with F > 2σ(F). The mineral with the idealized formula Na15(Ca3Mn3)Zr3(Fe,Zr)3(Si,Ti)(Si,Nb)[Si3O9]2[Si9O27]2O2(OH,F,Cl)2·2H2O is a Sr-containing analogue of oneillite with a low niobium content and a predominance of silicon both in the M3 and M4 positions. The unit-cell parameters are a = 14.192(2) Å, c = 30.170(5) Å, V = 5262.74 Å3. Within the P3 model, in addition to the oneillite-type ring [Ca–Mn], the eudialyte ring [Ca–Ca] and the ring of the composition [Na–(Ca,Sr)] are also established. The crystallochemical role of strontium in minerals of the eudialyte group is analyzed.